Info: An Introduction
*********************

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

There are two primary Info readers: info, a stand-alone program designed just to read Info files (see What is Info? (GNU Info)), and the info package in GNU Emacs, a general-purpose editor.  At present, only the Emacs reader supports using a mouse.

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

To read about advanced Info commands, type n twice.  This brings you to Advanced Info Commands, skipping over the `Getting Started' chapter.

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

Copyright © 1989, 1992, 1996--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.''

Getting Started
***************

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

Starting Info on a Small Screen
===============================

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 the entire text you are looking at fits on the screen, the text All will be displayed at the bottom of the screen.  In the stand-alone Info reader, it is displayed at the bottom right corner of the screen; in Emacs, it is displayed on the modeline.  If you see the text 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 SPC, the Space bar.  To move back up, press the key labeled Backspace or DEL (on some keyboards, this key might be labeled Delete).

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

     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
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     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

If you have managed to get here, go back to the beginning with DEL (or BACKSPACE), and come back here again, then you understand the about the Space and Backspace keys.  So now type an 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.

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 info.

Right now you are looking at one 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 Help in the file info.

The top line of a node is its header.  This node's header (look at it now) says that the Next node after this one is the node called 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 displayed with a special typeface, and remains at the top of the window all the time even if you scroll through the node.

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

Now it is time to move on to the Next node, named Help-P.

     >> Type n to move there.  Type just one character;
        do not type the quotes and do not type a RET afterward.

>> in the margin means it is really time to try a command.

     >> If you are in Emacs and have a mouse, and if you already practiced
        typing n to get to the next node, click now with the left
        mouse button on the Next link to do the same ``the mouse way''.

Returning to the Previous node
==============================

This node is called Help-P.  The Previous node, as you see, is Help, which is the one you just came from using the n command.  Another n command now would take you to the next node, Help-^L.

     >> But do not type n yet.  First, try the p command, or
        (in Emacs) click on the Prev link.  That takes you to
        the Previous node.  Then use n to return here.

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

This all probably seems insultingly simple so far, but 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.

     >> Now do an n, or (in Emacs) click the middle mouse button on
        the Next link, to get to the node Help-^L and learn more.

The Space, DEL, B and ^L commands
=================================

This node's mode line tells you that you are now at node Help-^L, and the header line tells you that p would get you back to 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 text Top rather than All near the bottom of the screen.

The SPC, BACKSPACE (or DEL) (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 ENTER or 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 Backspace or <- or DEL, or sometimes Delete.) and b commands exist to allow you to ``move around'' in a node that does not all fit on the screen at once.  SPC moves forward, to show what was below the bottom of the screen.  DEL or 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).

     >> Now try typing a SPC (afterward, type a BACKSPACE to
        return here).

When you type the SPC, the two lines that were at the bottom of the screen appear at the top, followed by more lines.  DEL or BACKSPACE takes the two lines from the top and moves them to the bottom, 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 Next, Prev, and Up links, and you can conveniently go to one of these links at any time by clicking the middle mouse button on the link.

SPC and DEL not only move forward and backward through the current node.  They also move between nodes.  SPC at the end of a node moves to the next node; DEL (or 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 SPC, and move backward through the entire manual from bottom to top by typing DEL (or BACKSPACE).

In this sequence, a node's subnodes appear following their parent. If a node has a menu, 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, SPC takes you to the next node or to the parent's next node.

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

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

     >> Type C-l now.

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

     >> 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 SPC one or more times.

You have just learned a considerable number of commands.  If you want to use one but have trouble remembering which, you should type ?, which displays a brief list of commands.  When you are finished looking at the list, make it go away by typing SPC repeatedly.

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

(If you are using the stand-alone Info reader, type C-x 0 to return here, that is---press and hold CTRL, type an x, then release CTRL and x, and press 0; that's 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 SPC and 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.

     >> Now type n, or click the middle mouse button on the Next link,
        to visit the next node.

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 ] now.

In Emacs, certain text that appears in the stand-alone version is normally hidden, technically because it has the 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.

You can make invisible text visible by using the command 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 always see the invisible text, you can set Info-hide-note-references to 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 display property.  Only the invisibility property is affected by Visible mode.  When, in this tutorial, we refer to the Emacs behavior, we mean the default Emacs behavior.

Now type ], to learn about the ] and [ commands.

The ] and [ commands
--------------------

If you type n now, you get an error message saying that this node has no next node.  Similarly, if you type 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 n and p carry you to the next and previous node 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 n or p could move to.

If you systematically move through a manual by typing n, you run the risk of skipping many nodes.  You do not run this risk if you systematically use SPC, because, when you scroll to the bottom of a node and type another SPC, then this carries you to the following node in the manual 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 ].

Similarly, 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 [.

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

Now type ] to go to the next node and learn about menus.

Menus and the m command
=======================

With only the n (next), p (previous), SPC, BACKSPACE, ] and [ 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 * 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 * identifies one subtopic.  The line usually contains a brief name for the subtopic (followed by a :, 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 * have no special meaning---they are only for the human reader's benefit and do not define additional subtopics.  Here is an example:

     * Foo:  Node about FOO.      This tells about FOO.

The subtopic name is Foo, and the node describing it is 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 * Menu:.  Also, in a real menu item, the * would appear at the very start of the line.  This is why the ``normally hidden'' text in Emacs, namely : 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:

     * Foo::   This tells about FOO.

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

     >> Now use SPC to find the menu in this node, then come back to
        the front with a b and some SPCs.  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
        m command is not available.

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

The command to go to one of the subnodes is 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 m command is different: it needs to know the name of the subtopic.  Once you have typed 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 n or b or SPC or 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 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.

The command to go to a subnode via a menu is m.  After you type the m, the line at the bottom of the screen says Menu item: . You must then type the name of the subtopic you want, and end it with a RET.

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.

You can also use the completion feature to help enter the subtopic name.  If you type the 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 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:

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

     >>  Now type just an m and see what happens:

Now you are ``inside'' an 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 m by typing Control-g.

     >> Try that now;  notice the bottom line clear.

     >> Then type another m.

     >> Now type BAR, the item name.  Do not type RET yet.

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

     >> Press DEL to cancel the R.  You could type another R
        to replace it.  But you do not have to, since BA is a valid
        abbreviation.

     >> Now you are ready to go.  Type a RET.

After visiting Help-FOO, you should return here.

Another way to move to the menu subtopic lines and between them is to type TAB.  Each time you type a TAB, you move to the next subtopic line.  To move to a previous subtopic line in the stand-alone reader, type M-TAB---that is, press and hold the META key and then press TAB.  (On some keyboards, the META key might be labeled Alt.)  In Emacs Info, type S-TAB to move to a previous subtopic line (press and hold the Shift key and then press TAB).

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

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 * and the colon : 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.

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 Mouse-2 with the current position of the mouse pointer (on subtopic in the menu) will go to that subtopic.

More generally, 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 f, in a menu it acts like m, on the node's header line it acts like n, p, or u, etc.  At end of the node's text Mouse-2 moves to the next node, or up if there's no next node.

     >> Type n to see more commands.

The u command
-------------

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

You can go back to the node Help-M by typing the command u for ``Up''.  This puts you at the menu subtopic line pointing to the subnode that the u command brought you from.  (Some Info readers may put you at the front of the node instead---to get back to where you were reading, you have to type some SPCs.)

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

     >> Now type u to move back up to Help-M.

Following Cross-References
==========================

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

You can follow a cross reference by moving the cursor to it and press RET, just as in a menu.  In Emacs, you can also click Mouse-1 on a cross reference to follow it; 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.

Another way to follow a cross reference is to type f and then specify the name of the cross reference (in this case, Cross) as an argument.  For this command, it does not matter where the cursor was.  If the cursor is on or near a cross reference, f suggests that reference name in parentheses as the default; typing RET will follow that reference.  However, if you type a different reference name, f will follow the other reference which has that name.

     >> Type f, followed by Cross, and then RET.

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

To get a list of all the cross references in the current node, you can type ? after an f.  The 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 Control-g to cancel the f.

     >> Type f? to get a list of the cross references in this node.  Then
        type a Control-g and see how the f gives up.

The TAB, M-TAB and S-TAB keys, 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: see Overview of Texinfo (Texinfo: The GNU Documentation Format).  (After following this link, type l to get back to this node.)  Here the name texinfo between parentheses refers to the file name.  This file name appears in cross references and node names if it differs from the current file, so you can always know that you are going to be switching to another manual and which one.

However, Emacs normally hides some other text in cross-references. If you put your mouse over the cross reference, then the information appearing in a separate box (tool tip) or in the echo area will show the full cross-reference including the file name and the node name of the cross reference.  If you have a mouse, just leave it over the cross reference see Overview of Texinfo (Texinfo: The GNU Documentation Format), and watch what happens.  If you always like to have that information visible without having to move your mouse over the cross reference, use M-x visible-mode, or set Info-hide-note-references to a value other than t (see Emacs Info Variables).

     >> Now type n to learn more commands.

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 containing little but a menu.  The menu has one menu item for each topic listed in the index.  (As a special feature, menus for indices may also include the line number within the node of the index entry. This allows Info readers to go to the exact line of an entry, not just the start of the containing node.)

You can get to the index from the main menu of the file with the m command and the name of the index node; then you can use the m command again in the index node to go to the node that describes the topic you want.

There is also a short-cut Info command, 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. See Search Index, for a full explanation.

If you have been moving around to different nodes and wish to retrace your steps, the l command (l for 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 l command revisits nodes in the history list; each successive l command moves one step back through the history.

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

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

You can use the r command (Info-history-forward in Emacs) to revisit nodes in the history list in the forward direction, so that r will return you to the node you came from by typing l.

The L command (Info-history in Emacs) creates a virtual node that contains a list of all nodes you visited.  You can select a previously visited node from this menu to revisit it.

The d command (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.

     >> Try doing a d, then do an l to return here (yes,
        do return).

The t command moves to the 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 t is Info-top-node.

     >> Now type n to see the last node of the course.

See Advanced, for more advanced Info features.

Quitting Info
=============

To get out of Info, back to what you were doing before, type q for Quit.  This runs 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 Advanced.

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.

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

Advanced Info Commands
**********************

This chapter describes various advanced Info commands.  (If you are using a stand-alone Info reader, there are additional commands specific to it, which are documented in several chapters of GNU Info.)

One advanced command useful with most of the others described here is C-q, which ``quotes'' the next character so that it is entered literally (see Inserting Text (The GNU Emacs Manual)).  For example, pressing ? ordinarily brings up a list of completion possibilities.  If you want to (for example) search for an actual ? character, the simplest way is to insert it using C-q ?.  This works the same in Emacs and stand-alone Info.

s searches Info documents
=========================

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 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 text or its indices.

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

Instead of using s in Emacs Info and in the stand-alone Info, you can use an incremental search started with C-s or C-r. It can search through multiple Info nodes.  See Incremental Search (The GNU Emacs Manual).  In Emacs, you can disable this behavior by setting the variable Info-isearch-search to nil (see Emacs Info Variables).

i searches the indices for specific subjects
============================================

Since most topics in the manual should be indexed, you should try the index search first before the text search.  The 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 , one or more times to go through additional index entries which match your subject.

The i command and subsequent , commands find all index entries which include the string you typed 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 Info shows in the echo area before looking at the node it displays.

Since 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 TAB).  If you want to catch index entries that refer to ``complete,'' ``completion,'' and ``completing,'' you could type icompletRET.

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 i prompts you for a topic.  For example, if you want to read the description of what the C-l key does, type iC-lRET literally.

Emacs provides the command Info-virtual-index, bound to the I key.  This behaves like i, but constructs a virtual info node displaying the results of an index search, making it easier to select the one you want.

If you aren't sure which manual documents the topic you are looking for, try the M-x info-apropos command in Emacs, or the M-x index-apropos command in the stand-alone reader.  It prompts for a string and then looks up that string in all the indices of all the Info documents installed on your system.

g goes to a node by name
========================

If you know a node's name, you can go there by typing g, the name, and RET.  Thus, gTopRET would go to the node called Top in this file.  (This is equivalent to t, see Help-Int.)  gGo to nodeRET would come back here.

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

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, g(dir)TopRET would go to the Info Directory node, which is the node Top in the Info file dir.  Likewise, g(emacs)TopRET (or just g(emacs)RET) goes to the top node of the Emacs manual.

The node name * specifies the whole file.  So you can look at all of the current file by typing g*RET or all of any other file with g(FILENAME)*RET.

1--9 choose a menu subtopic by its number
=========================================

If you begrudge each character of type-in which your system requires, you might like to use the commands 1, 2, 3, 4, ..., 9.  They are short for the m command together with a name of a menu subtopic.  1 goes through the first item in the current node's menu; 2 goes through the second item, etc. In the stand-alone reader, 0 goes through the last menu item; this is so you need not count how many entries are there.

If your display supports multiple fonts, colors or underlining, and you are using Emacs's Info mode to read Info files, the third, sixth and ninth menu items have a * that stands out, either in color or in some other attribute, such as underline; this makes it easy to see at a glance which number to use for an item.

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

M-n creates a new independent Info buffer in Emacs
==================================================

If you are reading Info in Emacs, you can select a new independent Info buffer in a new Emacs window by typing M-n.  The new buffer starts out as an exact copy of the old one, but you will be able to move independently between nodes in the two buffers.  (In Info mode, M-n runs the Emacs command clone-buffer.)

In Emacs Info, you can also produce new Info buffers by giving a numeric prefix argument to the m and g commands.  C-u m and C-u g go to a new node in exactly the same way that m and g do, but they do so in a new Info buffer which they select in another window.

Another way to produce new Info buffers in Emacs is to use a numeric prefix argument for the C-h i command (info) which switches to the Info buffer with that number.  Thus, C-u 2 C-h i switches to the buffer *info*<2>, creating it if necessary.

If you have created many Info buffers in Emacs, you might find it difficult to remember which buffer is showing which manual.  You can use the command M-x info-display-manual to show an Info manual by name, reusing an existing buffer if there is one.

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 init file.  See Examining and Setting Variables (The GNU Emacs Manual).  The stand-alone Info reader program has its own set of variables, described in Manipulating Variables (GNU Info).

Info-directory-list
     The list of directories to search for Info files.  Each element is a string (directory name) or nil (try default directory).  If not initialized Info uses the environment variable INFOPATH to initialize it, or Info-default-directory-list if there is no 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 INFOPATH environment variable, since that applies to both programs.

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

Info-mode-hook
     Hooks run when Info-mode is called.  By default, it contains the hook turn-on-font-lock which enables highlighting of Info files.  You can change how the highlighting looks by customizing the faces info-node, info-xref, info-xref-visited, info-header-xref, info-header-node, info-menu-header, info-menu-star, and info-title-N (where N is the level of the section, a number between 1 and 4).  To customize a face, type M-x customize-face RET FACE RET, where FACE is one of the face names listed here.

Info-fontify-maximum-menu-size
     Maximum size of menu to fontify if font-lock-mode is non-nil.

Info-fontify-visited-nodes
     If non-nil, menu items and cross-references pointing to visited nodes are displayed in the info-xref-visited face.

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

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 nil.  Setting it to a value that is neither nil nor t produces an intermediate behavior, hiding a limited amount of text, but showing all text that could potentially be useful.

Info-scroll-prefer-subnodes
     If set to a non-nil value, SPC and BACKSPACE (or 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 SPC moves to a subnode indicated by the following menu item.  Setting this option to 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 nil.

Info-isearch-search
     If non-nil, isearch in Info searches through multiple nodes.

Info-enable-active-nodes
     When set to a non-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 DEL character) and an execute:  tag, like this:

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

Info for Experts
****************

This chapter explains how to write an Info file by hand.  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.

The makeinfo command converts a Texinfo file into an Info file; texinfo-format-region and texinfo-format-buffer are GNU Emacs functions that do the same.

See Overview of Texinfo (Texinfo: The GNU Documentation Format), for how to write a Texinfo file.

See Creating an Info File (Texinfo: The GNU Documentation Format), for how to create an Info file from a Texinfo file.

See Installing an Info File (Texinfo: The GNU Documentation Format), for how to install an Info file after you have created one.

However, if you want to edit an Info file manually and install it manually, here is how.

Adding a new node to Info
=========================

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

 1. Create some nodes, in some file, to document that topic.

 2. Put that topic in the menu in the directory.  See Menu.

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

The ^_ starting a node must be followed by a newline or a ^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 Next, Previous, and Up nodes (if there are any).  As you can see, this node's Up node is the node Expert Info.  The Next node is Menus.

The keywords Node, Next, Previous, and 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.

A node name has two forms.  A node in the current file is named by what appears after the Node:  in that node's first line.  For example, this node's name is Add.  A node in another file is named by (FILENAME)NODE-WITHIN-FILE, as in (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 (FILENAME)Top can be abbreviated to just (FILENAME).  By convention, the name Top is used for the ``highest'' node in any single file---the node whose Up points out of the file.  The Directory node is (dir), it points to a file dir which holds a large menu listing all the Info documents installed on your site.  The Top node of a document file listed in the Directory should have an Up: (dir) in it.

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

The 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 Next, Previous and Up names may contain them.  In this node, since the 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.

How to Create Menus
===================

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

A menu begins with a line starting with * Menu:.  The rest of the line is a comment.  After the starting line, every line that begins with a *  lists a single topic.  The name of the topic---what the user must type at the 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 Next, Previous and 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 * 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 Up: pointing at the superior.  It is often useful to arrange all or most of the subnodes in a sequence of Next and 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 (dir)Top---that is, node Top in file .../info/dir.  You can put new entries in that menu just like any other menu.  The Info Directory is not the same as the file directory called 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 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 Top; the other contains the node Help which the h command goes to.  In fact, since there is no garbage collector on the node graph, 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.

Creating Cross References
=========================

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 *note instead of *. It cannot be terminated by a ), because )'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:

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

These are just examples.  The places they ``lead to'' do not really exist!

The node reached by the cross reference in Info
-----------------------------------------------

This is the node reached by the cross reference named 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 Next, Previous or Up links pointing back to where you came from.  In general, the l (el) command is the only way to get back there.

     >> Type l to return to the node where the cross reference was.

Tags Tables for 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.

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

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 Info-tagify command again.

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

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

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 DEL character, and the character position in the file of the beginning of the node.

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 Next, Previous, and Up is checked, as is every menu item and every cross reference.  In addition, any Next which does not have a 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.

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

GNU Free Documentation License
******************************

     [file doclicense.texi not included]

Index
*****

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