Don't compile sys_select on systems that don't need it.

[emacs.git] / man / info.texi

\input texinfo    @c -*-texinfo-*-
@comment %**start of header
@setfilename info.info
@settitle Info
@syncodeindex fn cp
@syncodeindex vr cp
@syncodeindex ky cp
@comment %**end of header
@comment $Id: info.texi,v 1.37 2003/10/27 00:01:25 karl Exp $

@copying
This file describes how to use Info, the on-line, menu-driven GNU
documentation system.

Copyright (C) 1989, 1992, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003
Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 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'' in the Emacs manual.

(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
this GNU Manual, like GNU software.  Copies published by the Free
Software Foundation raise funds for GNU development.''

This document is part of a collection distributed under the GNU Free
Documentation License.  If you want to distribute this document
separately from the collection, you can do so by adding a copy of the
license to the document, as described in section 6 of the license.
@end quotation
@end copying

@dircategory Texinfo documentation system
@direntry
* Info: (info).         How to use the documentation browsing system.
@end direntry

@titlepage
@title Info
@subtitle The online, hyper-text GNU documentation system
@author Brian Fox
@author and the GNU Texinfo community
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@ifnottex
@node Top
@top Info: An Introduction

The GNU Project distributes most of its on-line manuals in the
@dfn{Info format}, which you read using an @dfn{Info reader}.  You are
probably using an Info reader to read this now.

@ifinfo
If you are new to the Info reader and want to learn how to use it,
type the command @kbd{h} now.  It brings you to a programmed
instruction sequence.

To read about expert-level Info commands, type @kbd{n} twice.  This
brings you to @cite{Info for Experts}, skipping over the `Getting
Started' chapter.
@end ifinfo
@end ifnottex

@menu
* Getting Started::             Getting started using an Info reader.
* Expert Info::                 Info commands for experts.
* Creating an Info File::       How to make your own Info file.
* Index::                       An index of topics, commands, and variables.
@end menu

@node Getting Started, Expert Info, Top, Top
@comment  node-name,  next,  previous,  up
@chapter Getting Started

This first part of the Info manual describes how to get around inside
of Info.  The second part of the manual describes various advanced
Info commands, and how to write an Info as distinct from a Texinfo
file.  The third part briefly explains how to generate Info files from
Texinfo files.

@ifnotinfo
This manual is primarily designed for browsing with an Info reader
program on a computer, so that you can try Info commands while reading
about them.  Reading it on paper or with an HTML browser is less
effective, since you must take it on faith that the commands described
really do what the manual says.  By all means go through this manual
now that you have it; but please try going through the on-line version
as well.

@cindex Info reader, how to invoke
@cindex entering Info
There are two ways of looking at the online version of this manual:

@enumerate
@item
Type @code{info} at your shell's command line.  This approach uses a
stand-alone program designed just to read Info files.

@item
Type @code{emacs} at the command line; then type @kbd{C-h i}
(@kbd{Control-h}, followed by @kbd{i}).  This approach uses the Info
mode of the Emacs program, an editor with many other capabilities.
@end enumerate

In either case, then type @kbd{mInfo} (just the letters), followed by
@key{RET}---the ``Return'' or ``Enter'' key.  At this point, you should
be ready to follow the instructions in this manual as you read them on
the screen.
@c FIXME! (pesch@cygnus.com, 14 dec 1992)
@c Is it worth worrying about what-if the beginner goes to somebody
@c else's Emacs session, which already has an Info running in the middle
@c of something---in which case these simple instructions won't work?
@end ifnotinfo

@menu
* Help-Small-Screen::   Starting Info on a Small Screen
* Help::                How to use Info
* Help-P::              Returning to the Previous node
* Help-^L::             The Space, DEL, B and ^L commands.
* Help-Inv::            Invisible text in Emacs Info.
* Help-M::              Menus
* Help-Xref::           Following cross-references
* Help-Int::            Some intermediate Info commands
* Help-Q::              Quitting Info
@end menu

@node Help-Small-Screen
@section Starting Info on a Small Screen

@ifnotinfo
(In Info, you only see this section if your terminal has a small
number of lines; most readers pass by it without seeing it.)
@end ifnotinfo

@cindex small screen, moving around
Since your terminal has a relatively small number of lines on its
screen, it is necessary to give you special advice at the beginning.

If you see the text @samp{--All----} near the bottom right corner
of the screen, it means the entire text you are looking at fits on the
screen.  If you see @samp{--Top----} instead, it means that there is
more text below that does not fit.  To move forward through the text
and see another screen full, press @key{SPC}, the Space bar.  To move
back up, press the key labeled @samp{Backspace} or @samp{DEL} (on some
keyboards, this key might be labeled @samp{Delete}).

@ifinfo
Here are 40 lines of junk, so you can try @key{SPC} and @key{DEL} and
see what they do.  At the end are instructions of what you should do
next.

@format
This is line 20
This is line 21
This is line 22
This is line 23
This is line 24
This is line 25
This is line 26
This is line 27
This is line 28
This is line 29
This is line 30
This is line 31
This is line 32
This is line 33
This is line 34
This is line 35
This is line 36
This is line 37
This is line 38
This is line 39
This is line 40
This is line 41
This is line 42
This is line 43
This is line 44
This is line 45
This is line 46
This is line 47
This is line 48
This is line 49
This is line 50
This is line 51
This is line 52
This is line 53
This is line 54
This is line 55
This is line 56
This is line 57
This is line 58
This is line 59
@end format

If you have managed to get here, go back to the beginning with
@kbd{DEL} (or @key{BACKSPACE}), and come back here again, then you
understand the about the @samp{Space} and @samp{Backspace} keys.  So
now type an @kbd{n} ---just one character; don't type the quotes and
don't type the Return key afterward--- to get to the normal start of
the course.
@end ifinfo

@node Help, Help-P, Help-Small-Screen, Getting Started
@comment  node-name,  next,  previous,  up
@section How to use Info

You are talking to the program Info, for reading documentation.

  There are two ways to use Info: from within Emacs or as a
stand-alone reader that you can invoke from a shell using the command
@command{info}.

@cindex node, in Info documents
  Right now you are looking at one @dfn{Node} of Information.
A node contains text describing a specific topic at a specific
level of detail.  This node's topic is ``how to use Info''.  The mode
line says that this is node @samp{Help} in the file @file{info}.

@cindex header of Info node
  The top line of a node is its @dfn{header}.  This node's header
(look at it now) says that the @samp{Next} node after this one is the
node called @samp{Help-P}.  An advanced Info command lets you go to
any node whose name you know.  In the stand-alone Info reader program,
the header line shows the names of this node and the info file as
well.  In Emacs, the header line is duplicated in a special typeface,
and the duplicate remains at the top of the window all the time even
if you scroll through the node.

  Besides a @samp{Next}, a node can have a @samp{Previous} or an
@samp{Up} links, or both.  As you can see, this node has all of these
links.

@kindex n @r{(Info mode)}
  Now it is time to move on to the @samp{Next} node, named @samp{Help-P}.

@format
>> Type @kbd{n} to move there.  Type just one character;
   do not type the quotes and do not type a @key{RET} afterward.
@end format

@noindent
@samp{>>} in the margin means it is really time to try a command.

@format
>> If you are in Emacs and have a mouse, and if you already practiced
   typing @kbd{n} to get to the next node, click now with the middle
   mouse button on the @samp{Next} link to do the same ``the mouse way''.
@end format

@node Help-P, Help-^L, Help, Getting Started
@comment  node-name,  next,  previous,  up
@section Returning to the Previous node

@kindex p @r{(Info mode)}
This node is called @samp{Help-P}.  The @samp{Previous} node, as you see,
is @samp{Help}, which is the one you just came from using the @kbd{n}
command.  Another @kbd{n} command now would take you to the next
node, @samp{Help-^L}.

@format
>> But do not type @kbd{n} yet.  First, try the @kbd{p} command,
   or click the middle mouse button on the @samp{Prev} link.  That
   takes you to the @samp{Previous} node.  Then use @kbd{n} to return here.
@end format

  If you read this in Emacs, you will see an @samp{Info} item in the
menu bar, close to its right edge.  Clicking the mouse on the
@samp{Info} menu-bar item opens a menu of commands which include
@samp{Next} and @samp{Prev} (and also some others which you didn't yet
learn about).

  This all probably seems insultingly simple so far, but @emph{please
don't} start skimming.  Things will get complicated soon enough!
Also, please do not try a new command until you are told it is time
to.  You could make Info skip past an important warning that was
coming up.

@format
>> Now do an @kbd{n}, or click the middle mouse button on the @samp{Next}
   link, to get to the node @samp{Help-^L} and learn more.
@end format

@node Help-^L, Help-Inv, Help-P, Getting Started
@comment  node-name,  next,  previous,  up
@section The Space, DEL, B and ^L commands

  This node's mode line tells you that you are now at node
@samp{Help-^L}, and the header line tells you that @kbd{p} would get
you back to @samp{Help-P}.  The node's title is highlighted and may be
underlined as well; it says what the node is about.

  This is a big node and it does not all fit on your display screen.
You can tell that there is more that is not visible because you
can see the string @samp{--Top-----} rather than @samp{--All----} near
the bottom right corner of the screen.

@kindex SPC @r{(Info mode)}
@kindex DEL @r{(Info mode)}
@kindex BACKSPACE @r{(Info mode)}
@findex Info-scroll-up
@findex Info-scroll-down
  The @key{SPC}, @key{BACKSPACE} (or @key{DEL})@footnote{The key which
we call ``Backspace or DEL'' in this manual is labeled differently on
different keyboards.  Look for a key which is a little ways above the
@key{ENTER} or @key{RET} key and which you normally use outside Emacs
to erase the character before the cursor, i.e.@: the character you
typed last.  It might be labeled @samp{Backspace} or @samp{<-} or
@samp{DEL}, or sometimes @samp{Delete}.} and @kbd{b} commands exist to
allow you to ``move around'' in a node that does not all fit on the
screen at once.  @key{SPC} moves forward, to show what was below the
bottom of the screen.  @key{DEL} or @key{BACKSPACE} moves backward, to
show what was above the top of the screen (there is not anything above
the top until you have typed some spaces).

@format
>> Now try typing a @key{SPC} (afterward, type a @key{BACKSPACE} to
   return here).
@end format

  When you type the @key{SPC}, the two lines that were at the bottom of
the screen appear at the top, followed by more lines.  @key{DEL} or
@key{BACKSPACE} takes the two lines from the top and moves them to the
bottom, @emph{usually}, but if there are not a full screen's worth of
lines above them they may not make it all the way to the bottom.

  If you are reading this in Emacs, note that the header line is
always visible, never scrolling off the display.  That way, you can
always see the @samp{Next}, @samp{Prev}, and @samp{Up} links, and you
can conveniently go to one of these links at any time by
clicking the middle mouse button on the link.

@cindex reading Info documents top to bottom
@cindex Info documents as tutorials
  @key{SPC} and @key{DEL} not only move forward and backward through
the current node.  They also move between nodes.  @key{SPC} at the end
of a node moves to the next node; @key{DEL} (or @key{BACKSPACE}) at
the beginning of a node moves to the previous node.  In effect, these
commands scroll through all the nodes in an Info file as a single
logical sequence.  You can read an entire manual top to bottom by just
typing @key{SPC}, and move backward through the entire manual from
bottom to top by typing @key{DEL} (or @key{BACKSPACE}).

  In this sequence, a node's subnodes appear following their parent.
If a node has a menu, @key{SPC} takes you into the subnodes listed in
the menu, one by one.  Once you reach the end of a node, and have seen
all of its subnodes, @key{SPC} takes you to the next node or to the
parent's next node.

@kindex PAGEUP @r{(Info mode)}
@kindex PAGEDOWN @r{(Info mode)}
  Many keyboards nowadays have two scroll keys labeled @samp{PageUp}
and @samp{PageDown} (or maybe @samp{Prior} and @samp{Next}).  If your
keyboard has these keys, you can use them to move forward and backward
through the text of one node, like @key{SPC} and @key{BACKSPACE} (or
@key{DEL}).  However, @key{PAGEUP} and @key{PAGEDOWN} keys never
scroll beyond the beginning or the end of the current node.

@kindex C-l @r{(Info mode)}
  If your screen is ever garbaged, you can tell Info to display it
again by typing @kbd{C-l} (@kbd{Control-L}, that is---hold down
@key{CTRL} and type @kbd{L} or @kbd{l}).

@format
>> Type @kbd{C-l} now.
@end format

@kindex b @r{(Info mode)}
  To move back to the beginning of the node you are on, you can type
the @key{BACKSPACE} key (or @key{DEL}) many times.  You can also type
@kbd{b} just once.  @kbd{b} stands for ``beginning.''

@format
>> Try that now.  (We have put in enough verbiage to push this past
   the first screenful, but screens are so big nowadays that perhaps it
   isn't enough.  You may need to shrink your Emacs or Info window.)
   Then come back, by typing @key{SPC} one or more times.
@end format

  If your screen is very tall, all of this node might fit at once.  In
that case, @kbd{b} won't do anything.  But you could observe the
effect of the @kbd{b} key if you use a smaller window.

@kindex ? @r{(Info mode)}
@findex Info-summary
  You have just learned a considerable number of commands.  If you
want to use one but have trouble remembering which, you should type
a @kbd{?} (in Emacs it runs the @code{Info-summary} command) which
displays a brief list of commands.  When you are finished looking at
the list, make it go away by typing a @key{SPC} repeatedly.

@format
>> Type a @key{?} now.  Press @key{SPC} to see consecutive screenfuls of
   the list until finished.  Then type @key{SPC} several times.  If
   you are using Emacs, the help will then go away automatically.
@end format

  (If you are using the stand-alone Info reader, type @kbd{C-x 0} to
return here, that is---press and hold @key{CTRL}, type an @kbd{x},
then release @key{CTRL} and @kbd{x}, and press @kbd{0}---a zero, not
the letter ``o''.)

  From now on, you will encounter large nodes without warning, and
will be expected to know how to use @key{SPC} and @key{BACKSPACE} to
move around in them without being told.  Since not all terminals have
the same size screen, it would be impossible to warn you anyway.

@format
>> Now type @kbd{n}, or click the middle mouse button on the @samp{Next} link,
   to visit the next node.
@end format

@node Help-Inv, Help-M, Help-^L, Getting Started
@comment  node-name,  next,  previous,  up
@section Invisible text in Emacs Info

  Before discussing menus, we need to make some remarks that are only
relevant to users reading Info using Emacs.  Users of the stand-alone
version can skip this node by typing @kbd{]} now.

@cindex invisible text in Emacs
  In Emacs, certain text that appears in the stand-alone version is
normally hidden, technically because it has the @samp{invisibility}
property.  Invisible text is really a part of the text.  It becomes
visible (by default) after killing and yanking, it appears in printed
output, it gets saved to file just like any other text, and so on.
Thus it is useful to know it is there.

@findex visible-mode
You can make invisible text visible by using the command @kbd{M-x
visible-mode}.  Visible mode is a minor mode, so using the command a
second time will make the text invisible again.  Watch the effects of
the command on the ``menu'' below and the top line of this node.

If you prefer to @emph{always} see the invisible text, you can set
@code{Info-hide-note-references} to @code{nil}.  Enabling Visible mode
permanently is not a real alternative, because Emacs Info also uses
(although less extensively) another text property that can change the
text being displayed, the @samp{display} property.  Only the
invisibility property is affected by Visible mode.  When, in this
tutorial, we refer to the @samp{Emacs} behavior, we mean the
@emph{default} Emacs behavior.

Now type @kbd{]}, to learn about the @kbd{]} and @kbd{[} commands.

@menu
* ]:         Help-].               Node telling about ].
* stuff:     Help-].               Same node.
* Help-]::                         Yet again, same node.
@end menu

@node Help-], , , Help-Inv
@subsection The @kbd{]} and @kbd{[} commands

If you type @kbd{n} now, you get an error message saying that this
node has no next node.  Similarly, if you type @kbd{p}, the error
message tells you that there is no previous node.  (The exact message
depends on the Info reader you use.)  This is because @kbd{n} and
@kbd{p} carry you to the next and previous node @emph{at the same
level}.  The present node is contained in a menu (see next) of the
node you came from, and hence is considered to be at a lower level.
It is the only node in the previous node's menu (even though it was
listed three times). Hence it has no next or previous node that
@kbd{n} or @kbd{p} could move to.

If you systematically move through a manual by typing @kbd{n}, you run
the risk of skipping many nodes.  You do not run this risk if you
systematically use @kbd{@key{SPC}}, because, when you scroll to the
bottom of a node and type another @kbd{@key{SPC}}, then this carries
you to the following node in the manual @emph{regardless of level}.
If you immediately want to go to that node, without having to scroll
to the bottom of the screen first, you can type @kbd{]}.

Similarly, @kbd{@key{BACKSPACE}} carries you to the preceding node
regardless of level, after you scrolled to the beginning of the
present node.  If you want to go to the preceding node immediately,
you can type @kbd{[}.

For instance, typing this sequence will come back here in three steps:
@kbd{[ n [}.  To do the same backward, type @kbd{] p ]}.

Now type @kbd{]} to go to the next node and learn about menus.

@node Help-M, Help-Xref, Help-Inv, Getting Started
@comment  node-name,  next,  previous,  up
@section Menus and the @kbd{m} command

@cindex menus in an Info document
@cindex Info menus
  With only the @kbd{n} (next), @kbd{p} (previous), @kbd{@key{SPC}},
@kbd{@key{BACKSPACE}}, @kbd{]} and @kbd{[} commands for moving between
nodes, nodes are restricted to a linear sequence.  Menus allow a
branching structure.  A menu is a list of other nodes you can move to.
It is actually just part of the text of the node formatted specially
so that Info can interpret it.  The beginning of a menu is always
identified by a line which starts with @w{@samp{* Menu:}}.  A node
contains a menu if and only if it has a line in it which starts that
way.  The only menu you can use at any moment is the one in the node
you are in.  To use a menu in any other node, you must move to that
node first.

  After the start of the menu, each line that starts with a @samp{*}
identifies one subtopic.  The line usually contains a brief name for
the subtopic (followed by a @samp{:}, normally hidden in Emacs), the
name of the node that talks about that subtopic (again, normally
hidden in Emacs), and optionally some further description of the
subtopic.  Lines in the menu that do not start with a @samp{*} have no
special meaning---they are only for the human reader's benefit and do
not define additional subtopics.  Here is an example:

@example
* Foo:  Node about FOO.      This tells about FOO.
@end example

The subtopic name is Foo, and the node describing it is @samp{Node
about FOO}.  The rest of the line is just for the reader's
Information.  [[ But this line is not a real menu item, simply because
there is no line above it which starts with @w{@samp{* Menu:}}.  Also,
in a real menu item, the @samp{*} would appear at the very start of
the line.  This is why the ``normally hidden'' text in Emacs, namely
@samp{: Node about FOO.}, is actually visible in this example, even
when Visible mode is off.]]

  When you use a menu to go to another node (in a way that will be
described soon), what you specify is the subtopic name, the first
thing in the menu line.  Info uses it to find the menu line, extracts
the node name from it, and goes to that node.  The reason that there
is both a subtopic name and a node name is that the node name must be
meaningful to the computer and may therefore have to be ugly looking.
The subtopic name can be chosen just to be convenient for the user to
specify.  Often the node name is convenient for the user to specify
and so both it and the subtopic name are the same.  There is an
abbreviation for this:

@example
* Foo::   This tells about FOO.
@end example

@noindent
This means that the subtopic name and node name are the same; they are
both @samp{Foo}.  (The @samp{::} is normally hidden in Emacs.)

@format
>> Now use @key{SPC} to find the menu in this node, then come back to
   the front with a @kbd{b} and some @key{SPC}s.  As you see, a menu is
   actually visible in its node.  If you cannot find a menu in a node
   by looking at it, then the node does not have a menu and the
   @kbd{m} command is not available.
@end format

If you keep typing @key{SPC} once the menu appears on the screen, it
will move to another node (the first one in the menu).  If that
happens, type @key{BACKSPACE} to come back.

@kindex m @r{(Info mode)}
  The command to go to one of the subnodes is @kbd{m}.  This is very
different from the commands you have used: it is a command that
prompts you for more input.

  The Info commands you know do not need additional input; when you
type one of them, Info processes it instantly and then is ready for
another command.  The @kbd{m} command is different: it needs to know
the @dfn{name of the subtopic}.  Once you have typed @kbd{m}, Info
tries to read the subtopic name.

  Now, in the stand-alone Info, look for the line containing many
dashes near the bottom of the screen.  (This is the stand-alone
equivalent for the mode line in Emacs.)  There is one more line
beneath that one, but usually it is blank.  (In Emacs, this is the
echo area.)  When it is blank, Info is ready for a command, such as
@kbd{n} or @kbd{b} or @key{SPC} or @kbd{m}.  If that line contains
text ending in a colon, it means Info is reading more input for the
last command.  You can't type an Info command then, because Info is
trying to read input, not commands.  You must either give the input
and finish the command you started, or type @kbd{Control-g} to cancel
the command.  When you have done one of those things, the input entry
line becomes blank again.  Then you can type Info commands again.

@findex Info-menu
  The command to go to a subnode via a menu is @kbd{m}.  After you type
the @kbd{m}, the line at the bottom of the screen says @samp{Menu item: }.
You must then type the name of the subtopic you want, and end it with
a @key{RET}.  In Emacs, @kbd{m} runs the command @code{Info-menu}.

@cindex abbreviating Info subnodes
  You can abbreviate the subtopic name.  If the abbreviation is not
unique, the first matching subtopic is chosen.  Some menus put
the shortest possible abbreviation for each subtopic name in capital
letters, so you can see how much you need to type.  It does not
matter whether you use upper case or lower case when you type the
subtopic.  You should not put any spaces at the end, or inside of the
item name, except for one space where a space appears in the item in
the menu.

@cindex completion of Info node names
  You can also use the @dfn{completion} feature to help enter the
subtopic name.  If you type the @key{TAB} key after entering part of a
name, it will fill in more of the name---as much as Info can deduce
from the part you have entered.

  If you move the cursor to one of the menu subtopic lines, then you do
not need to type the argument: you just type a @key{RET}, and it
stands for the subtopic of the line you are on.  You can also click
the middle mouse button directly on the subtopic line to go there.

Here is a menu to give you a chance to practice.  This menu gives you
three ways of going to one place, Help-FOO:

@menu
* Foo:  Help-FOO.       A node you can visit for fun.
* Bar:  Help-FOO.       We have made two ways to get to the same place.
* Help-FOO::            And yet another!
@end menu

(Turn Visible mode on if you are using Emacs.)

@format
>>  Now type just an @kbd{m} and see what happens:
@end format

  Now you are ``inside'' an @kbd{m} command.  Commands cannot be used
now; the next thing you will type must be the name of a subtopic.

  You can change your mind about doing the @kbd{m} by typing
@kbd{Control-g}.

@format
>> Try that now;  notice the bottom line clear.
@end format

@format
>> Then type another @kbd{m}.
@end format

@format
>> Now type @kbd{BAR}, the item name.  Do not type @key{RET} yet.
@end format

  While you are typing the item name, you can use the @key{DEL} (or
@key{BACKSPACE}) key to cancel one character at a time if you make a
mistake.

@format
>> Press @key{DEL} to cancel the @samp{R}.  You could type another @kbd{R}
   to replace it.  But you do not have to, since @samp{BA} is a valid
   abbreviation.
@end format

@format
>> Now you are ready to go.  Type a @key{RET}.
@end format

  After visiting @samp{Help-FOO}, you should return here.

  Another way to move to the menu subtopic lines and between them is
to type @key{TAB}.  Each time you type a @key{TAB}, you move to the
next subtopic line.  To move to a previous subtopic line, type
@kbd{M-@key{TAB}}---that is, press and hold the @key{META} key and then
press @key{TAB}.  (On some keyboards, the @key{META} key might be labeled
@samp{Alt}.)

  Once you move cursor to a subtopic line, press @key{RET} to go to
that subtopic's node.

@cindex mouse support in Info mode
@kindex Mouse-2 @r{(Info mode)}
  If your terminal supports a mouse, you have yet another way of going
to a subtopic.  Move your mouse pointer to the subtopic line,
somewhere between the beginning @samp{*} and the colon @samp{:} which
ends the subtopic's brief name.  You will see the subtopic's name
change its appearance (usually, its background color will change), and
the shape of the mouse pointer will change if your platform supports
that.  After a while, if you leave the mouse on that spot, a small
window will pop up, saying ``Mouse-2: go to that node'', or the same
message may appear at the bottom of the screen.

  @kbd{Mouse-2} is the second button of your mouse counting from the
left---the middle button on a 3-button mouse.  (On a 2-button mouse,
you may have to press both buttons together to ``press the middle
button''.)  The message tells you pressing @kbd{Mouse-2} with the
current position of the mouse pointer (on subtopic in the menu) will
go to that subtopic.

@findex Info-mouse-follow-nearest-node
  More generally, @kbd{Mouse-2} in an Info buffer finds the nearest
link to another node and goes there.  For example, near a cross
reference it acts like @kbd{f}, in a menu it acts like @kbd{m}, on the
node's header line it acts like @kbd{n}, @kbd{p}, or @kbd{u}, etc.  At
end of the node's text @kbd{Mouse-2} moves to the next node, or up if
there's no next node.

@format
>> Type @kbd{n} to see more commands.
@end format

@node Help-FOO,  ,  , Help-M
@subsection The @kbd{u} command

  Congratulations!  This is the node @samp{Help-FOO}.  It has an @samp{Up}
pointer @samp{Help-M}, the node you just came from via the @kbd{m}
command.  This is the usual convention---the nodes you reach from a menu
have @samp{Up} nodes that lead back to the menu.  Menus move Down in the
tree, and @samp{Up} moves Up.  @samp{Previous}, on the other hand, is
usually used to ``stay on the same level but go backwards''.

@kindex u @r{(Info mode)}
@findex Info-up
  You can go back to the node @samp{Help-M} by typing the command
@kbd{u} for ``Up'' (the Emacs command run by @kbd{u} is
@code{Info-up}).  That puts you at the @emph{front} of the node---to
get back to where you were reading you have to type some @key{SPC}s.
(Some Info readers, such as the one built into Emacs, put you at the
same place where you were reading in @samp{Help-M}.)

  Another way to go Up is to click @kbd{Mouse-2} on the @samp{Up}
pointer shown in the header line (provided that you have a mouse).

@format
>> Now type @kbd{u} to move back up to @samp{Help-M}.
@end format

@node Help-Xref, Help-Int, Help-M, Getting Started
@comment  node-name,  next,  previous,  up
@section Following Cross-References

@cindex cross references in Info documents
  In Info documentation, you will see many @dfn{cross references}.
Cross references look like this: @xref{Help-Cross, Cross}.  That text
is a real, live cross reference, whose name is @samp{Cross} and which
points to the node named @samp{Help-Cross}.  (The node name is hidden
in Emacs.  Do @kbd{M-x visible-mode} to show or hide it.)

@kindex f @r{(Info mode)}
@findex Info-follow-reference
  There are two ways to follow a cross reference.  You can move the
cursor to it and press @key{RET}, just as in a menu.  @key{RET}
follows the cross reference that the cursor is on.  Or you can type
@kbd{f} and then specify the name of the cross reference (in this
case, @samp{Cross}) as an argument.  In Emacs Info, @kbd{f} runs
@code{Info-follow-reference},

  In the @kbd{f} command, you select the cross reference with its
name, so it does not matter where the cursor was.  If the cursor is on
or near a cross reference, @kbd{f} suggests that reference name in
parentheses as the default; typing @key{RET} will follow that
reference.  However, if you type a different reference name, @kbd{f}
will follow the other reference which has that name.

@format
>> Type @kbd{f}, followed by @kbd{Cross}, and then @key{RET}.
@end format

  As you enter the reference name, you can use the @key{DEL} (or
@key{BACKSPACE}) key to edit your input.  If you change your mind
about following any reference, you can use @kbd{Control-g} to cancel
the command.  Completion is available in the @kbd{f} command; you can
complete among all the cross reference names in the current node by
typing a @key{TAB}.

  To get a list of all the cross references in the current node, you
can type @kbd{?} after an @kbd{f}.  The @kbd{f} continues to await a
cross reference name even after displaying the list, so if you don't
actually want to follow a reference, you should type a @kbd{Control-g}
to cancel the @kbd{f}.

@format
>> Type @kbd{f?} to get a list of the cross references in this node.  Then
   type a @kbd{Control-g} and see how the @samp{f} gives up.
@end format

  The @key{TAB} and @kbd{M-@key{TAB}} key, which move between menu
items in a menu, also move between cross references outside of menus.

  Sometimes a cross reference (or a node) can lead to another file (in
other words another ``manual''), or, on occasion, even a file on a
remote machine (although Info files distributed with Emacs or the
stand-alone Info avoid using remote links).  Such a cross reference
looks like this: @xref{Top,, Overview of Texinfo, texinfo, Texinfo:
The GNU Documentation Format}.  (After following this link, type
@kbd{l} to get back to this node.)  Here the name @samp{texinfo}
between parentheses (shown in the stand-alone version) refers to the
file name.  This file name appears in cross references and node names
if it differs from the current file.  In Emacs, the file name is
hidden (along with other text).  (Use @kbd{M-x visible-mode} to show
or hide it.)

  The remainder of this node applies only to the Emacs version.  If
you use the stand-alone version, you can type @kbd{n} immediately.

  To some users, switching manuals is a much bigger switch than
switching sections.  These users like to know that they are going to
be switching to another manual (and which one) before actually doing
so, especially given that, if one does not notice, Info commands like
@kbd{t} (see the next node) can have confusing results.

  If you put your mouse over the cross reference and if the cross
reference leads to a different manual, then the information appearing
in a separate box (tool tip) or in the echo area, will mention the
file the cross reference will carry you to (between parentheses).
This is also true for menu subtopic names.  If you have a mouse, just
leave it over the @samp{Overview} cross reference above and watch what
happens.

  If you always like to have that information available without having
to move your mouse over the cross reference, set
@code{Info-hide-note-references} to a value other than t (@pxref{Emacs
Info Variables}).  You might also want to do that if you have a lot of
cross references to files on remote machines and have non-permanent or
slow access, since otherwise you might not be able to distinguish
between local and remote links.

@format
>> Now type @kbd{n} to learn more commands.
@end format

@node Help-Int, Help-Q, Help-Xref, Getting Started
@comment  node-name,  next,  previous,  up
@section Some intermediate Info commands

  The introductory course is almost over; please continue
a little longer to learn some intermediate-level commands.

  Most Info files have an index, which is actually a large node that
contains nothing but a menu.  The menu has one menu item for each
topic listed in the index.  You can find the index node from the main
menu of the file, with the @kbd{m} command; then you can use the
@kbd{m} command again in the index node to go to the node that
describes the topic.

  There is also a short-cut Info command, @kbd{i}, which does all of
that for you.  It searches the index for a given topic (a string) and
goes to the node which is listed in the index for that topic.
@xref{Info Search}, for a full explanation.

@kindex l @r{(Info mode)}
@findex Info-last
@cindex going back in Info mode
  If you have been moving around to different nodes and wish to
retrace your steps, the @kbd{l} command (@kbd{l} for @dfn{last}) will
do that, one node-step at a time.  As you move from node to node, Info
records the nodes where you have been in a special history list.  The
@kbd{l} command revisits nodes in the history list; each successive
@kbd{l} command moves one step back through the history.

  In Emacs, @kbd{l} runs the command @code{Info-last}.

@format
>> Try typing @kbd{p p n} and then three @kbd{l}'s, pausing in between
to see what each @kbd{l} does.  You should wind up right back here.
@end format

  Note the difference between @kbd{l} and @kbd{p}: @kbd{l} moves to
where @emph{you} last were, whereas @kbd{p} always moves to the node
which the header says is the @samp{Previous} node (from this node, the
@samp{Prev} link leads to @samp{Help-Xref}).

@kindex d @r{(Info mode)}
@findex Info-directory
@cindex go to Directory node
  The @kbd{d} command (@code{Info-directory} in Emacs) gets you
instantly to the Directory node.  This node, which is the first one
you saw when you entered Info, has a menu which leads (directly or
indirectly, through other menus), to all the nodes that exist.  The
Directory node lists all the manuals and other Info documents that
are, or could be, installed on your system.

@format
>> Try doing a @kbd{d}, then do an @kbd{l} to return here (yes,
   @emph{do} return).
@end format

@kindex t @r{(Info mode)}
@findex Info-top-node
@cindex go to Top node
  The @kbd{t} command moves to the @samp{Top} node of the manual.
This is useful if you want to browse the manual's main menu, or select
some specific top-level menu item.  The Emacs command run by @kbd{t}
is @code{Info-top-node}.

  Clicking @kbd{Mouse-2} on or near a cross reference also follows the
reference.  You can see that the cross reference is mouse-sensitive by
moving the mouse pointer to the reference and watching how the
underlying text and the mouse pointer change in response.

@format
>> Now type @kbd{n} to see the last node of the course.
@end format

  @xref{Expert Info}, for more advanced Info features.

@c If a menu appears at the end of this node, remove it.
@c It is an accident of the menu updating command.

@node Expert Info
@chapter Info for Experts

  This chapter describes various Info commands for experts.  (If you
are using a stand-alone Info reader, there are additional commands
specific to it, which are documented in several chapters of @ref{Top,,
GNU Info, info-stnd, GNU Info}.)

  This chapter also explains how to write an Info as distinct from a
Texinfo file.  (However, in most cases, writing a Texinfo file is
better, since you can use it to make a printed manual or produce other
formats, such as HTML and DocBook, as well as for generating Info
files.)  @xref{Top,, Overview of Texinfo, texinfo, Texinfo: The GNU
Documentation Format}.

@menu
* Advanced::             Advanced Info commands: g, e, and 1 - 9.
* Info Search::          How to search Info documents for specific subjects.
* Add::                  Describes how to add new nodes to the hierarchy.
                           Also tells what nodes look like.
* Menus::                How to add to or create menus in Info nodes.
* Cross-refs::           How to add cross-references to Info nodes.
* Tags::                 How to make tags tables for Info files.
* Checking::             Checking an Info File
* Emacs Info Variables:: Variables modifying the behavior of Emacs Info.
@end menu

@node Advanced, Info Search,  , Expert Info
@comment  node-name,  next,  previous,  up
@section Advanced Info Commands

Here are some more Info commands that make it easier to move around.

@unnumberedsubsec @kbd{g} goes to a node by name

@kindex g @r{(Info mode)}
@findex Info-goto-node
@cindex go to a node by name
  If you know a node's name, you can go there by typing @kbd{g}, the
name, and @key{RET}.  Thus, @kbd{gTop@key{RET}} would go to the node
called @samp{Top} in this file.  (This is equivalent to @kbd{t}, see
@ref{Help-Int}.)  @kbd{gAdvanced@key{RET}} would come back here.
@kbd{g} in Emacs runs the command @code{Info-goto-node}.

  Unlike @kbd{m}, @kbd{g} does not allow the use of abbreviations.
But it does allow completion, so you can type @key{TAB} to complete a
partial node name.

@cindex go to another Info file
  To go to a node in another file, you can include the file name in the
node name by putting it at the front, in parentheses.  Thus,
@kbd{g(dir)Top@key{RET}} would go to the Info Directory node, which is
the node @samp{Top} in the Info file @file{dir}.  Likewise,
@kbd{g(emacs)Top@key{RET}} goes to the top node of the Emacs manual.

  The node name @samp{*} specifies the whole file.  So you can look at
all of the current file by typing @kbd{g*@key{RET}} or all of any
other file with @kbd{g(@var{filename})@key{RET}}.

@unnumberedsubsec @kbd{1} -- @kbd{9} choose a menu subtopic by its number

@kindex 1 @r{through} 9 @r{(Info mode)}
@findex Info-nth-menu-item
@cindex select @var{n}'th menu item
  If you begrudge each character of type-in which your system requires,
you might like to use the commands @kbd{1}, @kbd{2}, @kbd{3}, @kbd{4},
@dots{}, @kbd{9}.  They are short for the @kbd{m} command together
with a name of a menu subtopic.  @kbd{1} goes through the first item
in the current node's menu; @kbd{2} goes through the second item, etc.
In the stand-alone reader, @kbd{0} goes through the last menu item;
this is so you need not count how many entries are there.  In Emacs,
the digit keys run the command @code{Info-nth-menu-item}.

  If your display supports multiple fonts, and you are using Emacs'
Info mode to read Info files, the @samp{*} for the fifth menu item
stands out, either in color or in some other attribute, such as
underline, and so is the @samp{*} for the ninth item; this makes it
easy to see at a glance which number to use for an item.

  Some terminals don't support colors or underlining.  If you need to
actually count items, it is better to use @kbd{m} instead, and specify
the name, or use @key{TAB} to quickly move between menu items.

@unnumberedsubsec @kbd{e} makes Info document editable

@kindex e @r{(Info mode)}
@findex Info-edit
@cindex edit Info document
  The Info command @kbd{e} changes from Info mode to an ordinary
Emacs editing mode, so that you can edit the text of the current node.
Type @kbd{C-c C-c} to switch back to Info.  The @kbd{e} command is allowed
only if the variable @code{Info-enable-edit} is non-@code{nil}.

  The @kbd{e} command only works in Emacs, where it runs the command
@code{Info-edit}.  The stand-alone Info reader doesn't allow you to
edit the Info file, so typing @kbd{e} there goes to the end of the
current node.

@node Info Search, Add, Advanced, Expert Info
@comment  node-name,  next,  previous,  up
@section How to search Info documents for specific subjects

@cindex searching Info documents
@cindex Info document as a reference
  The commands which move between and inside nodes allow you to read
the entire manual or its large portions.  But what if you need to find
some information in the manual as fast as you can, and you don't know
or don't remember in what node to look for it?  This need arises when
you use a manual as a @dfn{reference}, or when it is impractical to
read the entire manual before you start using the programs it
describes.

  Info has powerful searching facilities that let you find things
quickly.  You can search either the manual indices or its text.

@kindex i @r{(Info mode)}
@findex Info-index
  Since most subjects related to what the manual describes should be
indexed, you should try the index search first.  The @kbd{i} command
prompts you for a subject and then looks up that subject in the
indices.  If it finds an index entry with the subject you typed, it
goes to the node to which that index entry points.  You should browse
through that node to see whether the issue you are looking for is
described there.  If it isn't, type @kbd{,} one or more times to go
through additional index entries which match your subject.

  The @kbd{i} command finds all index entries which include the string
you typed @emph{as a substring}.  For each match, Info shows in the
echo area the full index entry it found.  Often, the text of the full
index entry already gives you enough information to decide whether it
is relevant to what you are looking for, so we recommend that you read
what Emacs shows in the echo area before looking at the node it
displays.

  Since @kbd{i} looks for a substring, you can search for subjects even
if you are not sure how they are spelled in the index.  For example,
suppose you want to find something that is pertinent to commands which
complete partial input (e.g., when you type @key{TAB}).  If you want
to catch index entries that refer to ``complete'', ``completion'', and
``completing'', you could type @kbd{icomplet@key{RET}}.

  Info documents which describe programs should index the commands,
options, and key sequences that the program provides.  If you are
looking for a description of a command, an option, or a key, just type
their names when @kbd{i} prompts you for a topic.  For example, if you
want to read the description of what the @kbd{C-f} key does, type
@kbd{iC-f@key{RET}}.  Here @kbd{C-f} are 3 literal characters
@samp{C}, @samp{-}, and @samp{f}, not the ``Control-f'' command key
you type inside Emacs to run the command bound to @kbd{C-f}.

  In Emacs, @kbd{i} runs the command @code{Info-index}.

@kindex s @r{(Info mode)}
@findex Info-search
  The @kbd{s} command allows you to search a whole file for a string.
It switches to the next node if and when that is necessary.  You
type @kbd{s} followed by the string to search for, terminated by
@key{RET}.  To search for the same string again, just @kbd{s} followed
by @key{RET} will do.  The file's nodes are scanned in the order
they are in in the file, which has no necessary relationship to the
order that they may be in the tree structure of menus and @samp{next}
pointers.  But normally the two orders are not very different.  In any
case, you can always do a @kbd{b} to find out what node you have
reached, if the header is not visible (this can happen, because @kbd{s}
puts your cursor at the occurrence of the string, not at the beginning
of the node).

@kindex M-s @r{(Info mode)}
  In Emacs, @kbd{Meta-s} is equivalent to @kbd{s}.  That is for
compatibility with other GNU packages that use @kbd{M-s} for a similar
kind of search command.  Both @kbd{s} and @kbd{M-s} run in Emacs the
command @code{Info-search}.


@node Add, Menus, Info Search, Expert Info
@comment  node-name,  next,  previous,  up
@section Adding a new node to Info

To add a new topic to the list in the Info directory, you must:

@enumerate
@item
Create some nodes, in some file, to document that topic.
@item
Put that topic in the menu in the directory.  @xref{Menus, Menu}.
@end enumerate

  Usually, the way to create the nodes is with Texinfo (@pxref{Top,,
Overview of Texinfo, texinfo, Texinfo: The GNU Documentation Format});
this has the advantage that you can also make a printed manual or HTML
from them.  You would use the @samp{@@dircategory} and
@samp{@@direntry} commands to put the manual into the Info directory.
However, if you want to edit an Info file manually and install it
manually, here is how.

@cindex node delimiters
  The new node can live in an existing documentation file, or in a new
one.  It must have a @samp{^_} character before it (invisible to the
user; this node has one but you cannot see it), and it ends with either
a @samp{^_}, a @samp{^L} (``formfeed''), or the end of file.@footnote{If
you put in a @samp{^L} to end a new node, be sure that there is a
@samp{^_} after it to start the next one, since @samp{^L} cannot
@emph{start} a node.  Also, a nicer way to make a node boundary be a
page boundary as well is to put a @samp{^L} @emph{right after} the
@samp{^_}.}

  The @samp{^_} starting a node must be followed by a newline or a
@samp{^L} newline, after which comes the node's header line.  The
header line must give the node's name (by which Info finds it), and
state the names of the @samp{Next}, @samp{Previous}, and @samp{Up}
nodes (if there are any).  As you can see, this node's @samp{Up} node
is the node @samp{Expert Info}.  The @samp{Next} node is @samp{Menus}.

@cindex node header line format
@cindex format of node headers
  The keywords @dfn{Node}, @dfn{Next}, @dfn{Previous}, and @dfn{Up}
may appear in any order, anywhere in the header line, but the
recommended order is the one in this sentence.  Each keyword must be
followed by a colon, spaces and tabs, and then the appropriate name.
The name may be terminated with a tab, a comma, or a newline.  A space
does not end it; node names may contain spaces.  The case of letters
in the names is insignificant.

@cindex node name format
@cindex Directory node
  A node name has two forms.  A node in the current file is named by
what appears after the @samp{Node: } in that node's first line.  For
example, this node's name is @samp{Add}.  A node in another file is
named by @samp{(@var{filename})@var{node-within-file}}, as in
@samp{(info)Add} for this node.  If the file name starts with ``./'',
then it is relative to the current directory; otherwise, it is
relative starting from the standard directory for Info files of your
site.  The name @samp{(@var{filename})Top} can be abbreviated to just
@samp{(@var{filename})}.  By convention, the name @samp{Top} is used
for the ``highest'' node in any single file---the node whose @samp{Up}
points out of the file.  The @samp{Directory} node is @file{(dir)}, it
points to a file @file{dir} which holds a large menu listing all the
Info documents installed on your site.  The @samp{Top} node of a
document file listed in the @samp{Directory} should have an @samp{Up:
(dir)} in it.

@cindex unstructured documents
  The node name @kbd{*} is special: it refers to the entire file.
Thus, @kbd{g*} shows you the whole current file.  The use of the
node @kbd{*} is to make it possible to make old-fashioned,
unstructured files into nodes of the tree.

  The @samp{Node:} name, in which a node states its own name, must not
contain a file name, since when Info searches for a node, it does not
expect a file name to be there.  The @samp{Next}, @samp{Previous} and
@samp{Up} names may contain them.  In this node, since the @samp{Up}
node is in the same file, it was not necessary to use one.

  Note that the nodes in this file have a file name in the header
line.  The file names are ignored by Info, but they serve as comments
to help identify the node for the user.

@node Menus, Cross-refs, Add, Expert Info
@comment  node-name,  next,  previous,  up
@section How to Create Menus

  Any node in the Info hierarchy may have a @dfn{menu}---a list of subnodes.
The @kbd{m} command searches the current node's menu for the topic which it
reads from the terminal.

@cindex menu and menu entry format
  A menu begins with a line starting with @w{@samp{* Menu:}}.  The
rest of the line is a comment.  After the starting line, every line
that begins with a @samp{* } lists a single topic.  The name of the
topic--what the user must type at the @kbd{m}'s command prompt to
select this topic---comes right after the star and space, and is
followed by a colon, spaces and tabs, and the name of the node which
discusses that topic.  The node name, like node names following
@samp{Next}, @samp{Previous} and @samp{Up}, may be terminated with a
tab, comma, or newline; it may also be terminated with a period.

  If the node name and topic name are the same, then rather than
giving the name twice, the abbreviation @samp{* @var{name}::} may be
used (and should be used, whenever possible, as it reduces the visual
clutter in the menu).

  It is considerate to choose the topic names so that they differ
from each other very near the beginning---this allows the user to type
short abbreviations.  In a long menu, it is a good idea to capitalize
the beginning of each item name which is the minimum acceptable
abbreviation for it (a long menu is more than 5 or so entries).

  The nodes listed in a node's menu are called its ``subnodes'', and it
is their ``superior''.  They should each have an @samp{Up:} pointing at
the superior.  It is often useful to arrange all or most of the subnodes
in a sequence of @samp{Next} and @samp{Previous} pointers so that
someone who wants to see them all need not keep revisiting the Menu.

  The Info Directory is simply the menu of the node @samp{(dir)Top}---that
is, node @samp{Top} in file @file{.../info/dir}.  You can put new entries
in that menu just like any other menu.  The Info Directory is @emph{not} the
same as the file directory called @file{info}.  It happens that many of
Info's files live in that file directory, but they do not have to; and
files in that directory are not automatically listed in the Info
Directory node.

  Also, although the Info node graph is claimed to be a ``hierarchy'',
in fact it can be @emph{any} directed graph.  Shared structures and
pointer cycles are perfectly possible, and can be used if they are
appropriate to the meaning to be expressed.  There is no need for all
the nodes in a file to form a connected structure.  In fact, this file
has two connected components.  You are in one of them, which is under
the node @samp{Top}; the other contains the node @samp{Help} which the
@kbd{h} command goes to.  In fact, since there is no garbage
collector, nothing terrible happens if a substructure is not pointed
to, but such a substructure is rather useless since nobody can
ever find out that it exists.

@node Cross-refs, Tags, Menus, Expert Info
@comment  node-name,  next,  previous,  up
@section Creating Cross References

@cindex cross reference format
  A cross reference can be placed anywhere in the text, unlike a menu
item which must go at the front of a line.  A cross reference looks
like a menu item except that it has @samp{*note} instead of @samp{*}.
It @emph{cannot} be terminated by a @samp{)}, because @samp{)}'s are
so often part of node names.  If you wish to enclose a cross reference
in parentheses, terminate it with a period first.  Here are two
examples of cross references pointers:

@example
*Note details: commands.  (See *note 3: Full Proof.)
@end example

@noindent
@emph{These are just examples.}  The places they ``lead to'' do not
really exist!

@menu
* Help-Cross::                  Target of a cross-reference.
@end menu


@node Help-Cross,  ,  , Cross-refs
@subsection The node reached by the cross reference in Info

  This is the node reached by the cross reference named @samp{Cross}.

  While this node is specifically intended to be reached by a cross
reference, most cross references lead to nodes that ``belong''
someplace else far away in the structure of an Info document.  So you
cannot expect this node to have a @samp{Next}, @samp{Previous} or
@samp{Up} links pointing back to where you came from.  In general, the
@kbd{l} (el) command is the only way to get back there.

@format
>> Type @kbd{l} to return to the node where the cross reference was.
@end format

@node Help-Q,  , Help-Int, Getting Started
@comment  node-name,  next,  previous,  up
@section Quitting Info

@kindex q @r{(Info mode)}
@findex Info-exit
@cindex quitting Info mode
  To get out of Info, back to what you were doing before, type @kbd{q}
for @dfn{Quit}.  This runs @code{Info-exit} in Emacs.

  This is the end of the basic course on using Info.  You have learned
how to move in an Info document, and how to follow menus and cross
references.  This makes you ready for reading manuals top to bottom,
as new users should do when they learn a new package.

  Another set of Info commands is useful when you need to find
something quickly in a manual---that is, when you need to use a manual
as a reference rather than as a tutorial.  We urge you to learn
these search commands as well.  If you want to do that now, follow this
cross reference to @ref{Info Search}.

Yet another set of commands are meant for experienced users; you can
find them by looking in the Directory node for documentation on Info.
Finding them will be a good exercise in using Info in the usual
manner.

@format
>> Type @kbd{d} to go to the Info directory node; then type
   @kbd{mInfo} and Return, to get to the node about Info and
   see what other help is available.
@end format


@node Tags, Checking, Cross-refs, Expert Info
@comment  node-name,  next,  previous,  up
@section Tags Tables for Info Files

@cindex tags tables in info files
  You can speed up the access to nodes of a large Info file by giving
it a tags table.  Unlike the tags table for a program, the tags table for
an Info file lives inside the file itself and is used
automatically whenever Info reads in the file.

@findex Info-tagify
  To make a tags table, go to a node in the file using Emacs Info mode and type
@kbd{M-x Info-tagify}.  Then you must use @kbd{C-x C-s} to save the
file.  Info files produced by the @code{makeinfo} command that is part
of the Texinfo package always have tags tables to begin with.

@cindex stale tags tables
@cindex update Info tags table
  Once the Info file has a tags table, you must make certain it is up
to date.  If you edit an Info file directly (as opposed to editing its
Texinfo source), and, as a result of deletion of text, any node moves back
more than a thousand characters in the file from the position
recorded in the tags table, Info will no longer be able to find that
node.  To update the tags table, use the @code{Info-tagify} command
again.

  An Info file tags table appears at the end of the file and looks like
this:

@example
^_^L
Tag Table:
File: info, Node: Cross-refs^?21419
File: info,  Node: Tags^?22145
^_
End Tag Table
@end example

@noindent
Note that it contains one line per node, and this line contains
the beginning of the node's header (ending just after the node name),
a @samp{DEL} character, and the character position in the file of the
beginning of the node.


@node Checking, Emacs Info Variables, Tags, Expert Info
@section Checking an Info File

When creating an Info file, it is easy to forget the name of a node when
you are making a pointer to it from another node.  If you put in the
wrong name for a node, this is not detected until someone tries to go
through the pointer using Info.  Verification of the Info file is an
automatic process which checks all pointers to nodes and reports any
pointers which are invalid.  Every @samp{Next}, @samp{Previous}, and
@samp{Up} is checked, as is every menu item and every cross reference.  In
addition, any @samp{Next} which does not have a @samp{Previous} pointing
back is reported.  Only pointers within the file are checked, because
checking pointers to other files would be terribly slow.  But those are
usually few.

@findex Info-validate
To check an Info file, do @kbd{M-x Info-validate} while looking at any
node of the file with Emacs Info mode.

@node Emacs Info Variables, , Checking, Expert Info
@section Emacs Info-mode Variables

The following variables may modify the behavior of Info-mode in Emacs;
you may wish to set one or several of these variables interactively, or
in your @file{~/.emacs} init file.  @xref{Examining, Examining and Setting
Variables, Examining and Setting Variables, emacs, The GNU Emacs
Manual}.  The stand-alone Info reader program has its own set of
variables, described in @ref{Variables,, Manipulating Variables,
info-stnd, GNU Info}.

@vtable @code
@item Info-directory-list
The list of directories to search for Info files.  Each element is a
string (directory name) or @code{nil} (try default directory).  If not
initialized Info uses the environment variable @env{INFOPATH} to
initialize it, or @code{Info-default-directory-list} if there is no
@env{INFOPATH} variable in the environment.

If you wish to customize the Info directory search list for both Emacs
info and stand-alone Info, it is best to set the @env{INFOPATH}
environment variable, since that applies to both programs.

@item Info-additional-directory-list
A list of additional directories to search for Info documentation files.
These directories are not searched for merging the @file{dir} file.

@item Info-fontify
When set to a non-@code{nil} value, enables highlighting of Info
files.  The default is @code{t}.  You can change how the highlighting
looks by customizing the faces @code{info-node}, @code{info-xref},
@code{info-header-xref}, @code{info-header-node}, @code{info-menu-5},
@code{info-menu-header}, and @code{info-title-@var{n}-face} (where
@var{n} is the level of the section, a number between 1 and 4).  To
customize a face, type @kbd{M-x customize-face @key{RET} @var{face}
@key{RET}}, where @var{face} is one of the face names listed here.

@item Info-use-header-line
If non-@code{nil}, Emacs puts in the Info buffer a header line showing
the @samp{Next}, @samp{Prev}, and @samp{Up} links.  A header line does
not scroll with the rest of the buffer, making these links always
visible.

@item Info-hide-note-references
As explained in earlier nodes, the Emacs version of Info normally
hides some text in menus and cross-references.  You can completely
disable this feature, by setting this option to @code{nil}.  Setting
it to a value that is neither @code{nil} nor @code{t} produces an
intermediate behavior, hiding a limited amount of text, but showing
all text that could potentially be useful.

@item Info-scroll-prefer-subnodes
If set to a non-@code{nil} value, @key{SPC} and @key{BACKSPACE} (or
@key{DEL}) keys in a menu visit subnodes of the current node before
scrolling to its end or beginning, respectively.  For example, if the
node's menu appears on the screen, the next @key{SPC} moves to a
subnode indicated by the following menu item.  Setting this option to
@code{nil} results in behavior similar to the stand-alone Info reader
program, which visits the first subnode from the menu only when you
hit the end of the current node.  The default is @code{nil}.

@item Info-enable-active-nodes
When set to a non-@code{nil} value, allows Info to execute Lisp code
associated with nodes.  The Lisp code is executed when the node is
selected.  The Lisp code to be executed should follow the node
delimiter (the @samp{DEL} character) and an @samp{execute: } tag, like
this:

@example
^_execute: (message "This is an active node!")
@end example

@item Info-enable-edit
Set to @code{nil}, disables the @samp{e} (@code{Info-edit}) command.  A
non-@code{nil} value enables it.  @xref{Add, Edit}.
@end vtable


@node Creating an Info File
@chapter Creating an Info File from a Texinfo File

@code{makeinfo} is a utility that converts a Texinfo file into an Info
file; @code{texinfo-format-region} and @code{texinfo-format-buffer} are
GNU Emacs functions that do the same.

@xref{Top,, Overview of Texinfo, texinfo, Texinfo: The GNU
Documentation Format}, to learn how to write a Texinfo file.

@xref{Creating an Info File,,, texinfo, Texinfo: The GNU Documentation
Format}, to learn how to create an Info file from a Texinfo file.

@xref{Installing an Info File,,, texinfo, Texinfo: The GNU
Documentation Format}, to learn how to install an Info file after you
have created one.

@node Index
@unnumbered Index

This is an alphabetical listing of all the commands, variables, and
topics discussed in this document.

@printindex cp

@bye

@ignore
   arch-tag: 965c1638-01d6-4156-9227-b10418b9d8e8
@end ignore