Two new recentf.el keybindings

[emacs.git] / doc / misc / faq.texi

\input texinfo   @c -*- mode: texinfo; -*-
@c %**start of header
@setfilename ../../info/efaq
@settitle GNU Emacs FAQ
@c %**end of header

@include emacsver.texi

@c This file is maintained by Romain Francoise <rfrancoise@gnu.org>.
@c Feel free to install changes without prior permission (but I'd
@c appreciate a notice if you do).

@copying
Copyright @copyright{} 2001-2012 Free Software Foundation, Inc.@*
Copyright @copyright{} 1994, 1995, 1996, 1997, 1998, 1999, 2000
Reuven M. Lerner@*
Copyright @copyright{} 1992, 1993 Steven Byrnes@*
Copyright @copyright{} 1990, 1991, 1992 Joseph Brian Wells@*

@quotation
This list of frequently asked questions about GNU Emacs with answers
(``FAQ'') may be translated into other languages, transformed into other
formats (e.g. Texinfo, Info, WWW, WAIS), and updated with new information.

The same conditions apply to any derivative of the FAQ as apply to the FAQ
itself.  Every copy of the FAQ must include this notice or an approved
translation, information on who is currently maintaining the FAQ and how to
contact them (including their e-mail address), and information on where the
latest version of the FAQ is archived (including FTP information).

The FAQ may be copied and redistributed under these conditions, except that
the FAQ may not be embedded in a larger literary work unless that work
itself allows free copying and redistribution.

[This version has been heavily edited since it was included in the Emacs
distribution.]
@end quotation
@end copying

@dircategory Emacs
@direntry
* Emacs FAQ: (efaq).            Frequently Asked Questions about Emacs.
@end direntry

@c The @titlepage stuff only appears in the printed version
@titlepage
@sp 10
@center @titlefont{GNU Emacs FAQ}

@c The following two commands start the copyright page.
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@node Top, FAQ notation, (dir), (dir)
@top The GNU Emacs FAQ

@c FIXME @today is just the day we ran `makeinfo'.
This is the GNU Emacs FAQ, last updated on @today{}.

This FAQ is maintained as a part of GNU Emacs.  If you find any errors,
or have any suggestions, please use @kbd{M-x report-emacs-bug} to report
them.

This is the version of the FAQ distributed with Emacs @value{EMACSVER}, and
mainly describes that version.  Although there is some information on
older versions, details about very old releases (now only of historical
interest) have been removed.  If you are interested in this, consult
either the version of the FAQ distributed with older versions of Emacs,
or the history of this document in the Emacs source repository.

Since Emacs releases are very stable, we recommend always running the
latest release.

This FAQ is not updated very frequently.  When you have a question about
Emacs, the Emacs manual is often the best starting point.

@ifnottex
@insertcopying
@end ifnottex

@menu
* FAQ notation::
* General questions::
* Getting help::
* Status of Emacs::
* Common requests::
* Bugs and problems::
* Compiling and installing Emacs::
* Finding Emacs and related packages::
* Major packages and programs::
* Key bindings::
* Alternate character sets::
* Mail and news::
* Concept index::
@end menu

@c ------------------------------------------------------------
@node FAQ notation
@chapter FAQ notation
@cindex FAQ notation

This chapter describes notation used in the GNU Emacs FAQ, as well as in
the Emacs documentation.  Consult this section if this is the first time
you are reading the FAQ, or if you are confused by notation or terms
used in the FAQ.

@menu
* Basic keys::
* Extended commands::
* Emacs manual::
* File-name conventions::
* Common acronyms::
@end menu

@node Basic keys
@section What do these mean: @kbd{C-h}, @kbd{C-M-a}, @key{RET}, @kbd{@key{ESC} a}, etc.?
@cindex Basic keys
@cindex Control key, notation for
@cindex @key{Meta} key, notation for
@cindex Control-Meta characters, notation for
@cindex @kbd{C-h}, definition of
@cindex @kbd{C-M-h}, definition of
@cindex @key{DEL}, definition of
@cindex @key{ESC}, definition of
@cindex @key{LFD}, definition of
@cindex @key{RET}, definition of
@cindex @key{SPC}, definition of
@cindex @key{TAB}, definition of
@cindex Notation for keys

@itemize @bullet

@item
@kbd{C-x}: press the @key{x} key while holding down the @key{Control} key

@item
@kbd{M-x}: press the @key{x} key while holding down the @key{Meta} key
(if your computer doesn't have a @key{Meta} key, @pxref{No Meta key})

@item
@kbd{M-C-x}: press the @key{x} key while holding down both @key{Control}
and @key{Meta}

@item
@kbd{C-M-x}: a synonym for the above

@item
@key{LFD}: Linefeed or Newline; same as @kbd{C-j}

@item
@key{RET}: @key{Return}, sometimes marked @key{Enter}; same as @kbd{C-m}

@item
@key{DEL}: @key{Delete}, usually @strong{not} the same as
@key{Backspace}; same as @kbd{C-?} (see @ref{Backspace invokes help}, if
deleting invokes Emacs help)

@item
@key{ESC}: Escape; same as @kbd{C-[}

@item
@key{TAB}: Tab; same as @kbd{C-i}

@item
@key{SPC}: Space bar

@end itemize

Key sequences longer than one key (and some single-key sequences) are
written inside quotes or on lines by themselves, like this:

@display
  @kbd{M-x frobnicate-while-foo RET}
@end display

@noindent
Any real spaces in such a key sequence should be ignored; only @key{SPC}
really means press the space key.

The @acronym{ASCII} code sent by @kbd{C-x} (except for @kbd{C-?}) is the value
that would be sent by pressing just @key{x} minus 96 (or 64 for
upper-case @key{X}) and will be from 0 to 31.  On Unix and GNU/Linux
terminals, the @acronym{ASCII} code sent by @kbd{M-x} is the sum of 128 and the
@acronym{ASCII} code that would be sent by pressing just @key{x}.  Essentially,
@key{Control} turns off bits 5 and 6 and @key{Meta} turns on bit
7@footnote{
DOS and Windows terminals don't set bit 7 when the @key{Meta} key is
pressed.}.

@kbd{C-?} (aka @key{DEL}) is @acronym{ASCII} code 127.  It is a misnomer to call
@kbd{C-?}  a ``control'' key, since 127 has both bits 5 and 6 turned ON.
Also, on very few keyboards does @kbd{C-?} generate @acronym{ASCII} code 127.
@c FIXME I cannot understand the previous sentence.

@inforef{Keys, Keys, emacs}, for more information.  (@xref{Emacs
manual}, for more information about Info.)

@node Extended commands
@section What does @file{M-x @var{command}} mean?
@cindex Extended commands
@cindex Commands, extended
@cindex M-x, meaning of

@kbd{M-x @var{command}} means type @kbd{M-x}, then type the name of the
command, then type @key{RET}.  (@xref{Basic keys}, if you're not sure
what @kbd{M-x} and @key{RET} mean.)

@kbd{M-x} (by default) invokes the command
@code{execute-extended-command}.  This command allows you to run any
Emacs command if you can remember the command's name.  If you can't
remember the command's name, you can type @key{TAB} and @key{SPC} for
completion, @key{?} for a list of possibilities, and @kbd{M-p} and
@kbd{M-n} (or up-arrow and down-arrow) to see previous commands entered.
An Emacs @dfn{command} is an @dfn{interactive} Emacs function.

@cindex @key{Do} key
Your system administrator may have bound other key sequences to invoke
@code{execute-extended-command}.  A function key labeled @kbd{Do} is a
good candidate for this, on keyboards that have such a key.

If you need to run non-interactive Emacs functions, see @ref{Evaluating
Emacs Lisp code}.

@node Emacs manual
@section How do I read topic XXX in the Emacs manual?
@cindex Emacs manual, reading topics in
@cindex Reading topics in the Emacs manual
@cindex Finding topics in the Emacs manual
@cindex Info, finding topics in

When we refer you to some @var{topic} in the Emacs manual, you can
read this manual node inside Emacs (assuming nothing is broken) by
typing @kbd{C-h i m emacs @key{RET} m @var{topic} @key{RET}}.

This invokes Info, the GNU hypertext documentation browser.  If you don't
already know how to use Info, type @key{?} from within Info.

If we refer to @var{topic}:@var{subtopic}, type @kbd{C-h i m emacs
@key{RET} m @var{topic} @key{RET} m @var{subtopic} @key{RET}}.

If these commands don't work as expected, your system administrator may
not have installed the Info files, or may have installed them
improperly.  In this case you should complain.

If you are reading this FAQ in Info, you can simply press @key{RET} on a
reference to follow it.

@xref{Getting a printed manual}, if you would like a paper copy of the
Emacs manual.

@node File-name conventions
@section What are @file{etc/GNU}, @file{src/config.h}, @file{site-lisp/default.el}, etc.?
@cindex File-name conventions
@cindex Conventions for file names
@cindex Directories and files that come with Emacs

These are files that come with Emacs.  The Emacs distribution is divided
into subdirectories; e.g. @file{etc}, @file{lisp}, and @file{src}.
Some of these (e.g. @file{etc} and @file{lisp}) are present both in
an installed Emacs and in the sources, but some (e.g. @file{src}) are
only found in the sources.

If you use Emacs, but don't know where it is kept on your system, start
Emacs, then type @kbd{C-h v data-directory @key{RET}}.  The directory
name displayed by this will be the full pathname of the installed
@file{etc} directory.  (This full path is recorded in the Emacs variable
@code{data-directory}, and @kbd{C-h v} displays the value and the
documentation of a variable.)

The location of your Info directory (i.e., where Info documentation
is stored) is kept in the variable @code{Info-default-directory-list}.  Use
@kbd{C-h v Info-default-directory-list @key{RET}} to see the value of
this variable, which will be a list of directory names.  The last
directory in that list is probably where most Info files are stored.  By
default, Emacs Info documentation is placed in @file{/usr/local/share/info}.

For information on some of the files in the @file{etc} directory,
@pxref{Informational files for Emacs}.

@node Common acronyms
@section What are FSF, LPF, GNU, RMS, FTP, and GPL?
@cindex FSF, definition of
@cindex LPF, definition of
@cindex GNU, definition of
@cindex RMS, definition of
@cindex Stallman, Richard, acronym for
@cindex Richard Stallman, acronym for
@cindex FTP, definition of
@cindex GPL, definition of
@cindex Acronyms, definitions for
@cindex Common acronyms, definitions for

@table @asis

@item FSF
Free Software Foundation

@item LPF
League for Programming Freedom

@item GNU
GNU's Not Unix

@item RMS
Richard Matthew Stallman

@item FTP
File Transfer Protocol

@item GPL
GNU General Public License

@end table

Avoid confusing the FSF and the LPF.  The LPF opposes
look-and-feel copyrights and software patents.  The FSF aims to make
high quality free software available for everyone.

The word ``free'' in the title of the Free Software Foundation refers to
``freedom,'' not ``zero cost.''  Anyone can charge any price for
GPL-covered software that they want to.  However, in practice, the
freedom enforced by the GPL leads to low prices, because you can always
get the software for less money from someone else, since everyone has
the right to resell or give away GPL-covered software.

@c ------------------------------------------------------------
@node General questions
@chapter General questions
@cindex General questions

This chapter contains general questions having to do with Emacs, the
Free Software Foundation, and related organizations.

@menu
* The LPF::
* Real meaning of copyleft::
* Guidelines for newsgroup postings::
* Newsgroup archives::
* Reporting bugs::
* Unsubscribing from Emacs lists::
* Contacting the FSF::
@end menu

@node The LPF
@section What is the LPF?
@cindex LPF, description of
@cindex League for Programming Freedom
@cindex Software patents, opposition to
@cindex Patents for software, opposition to

The LPF opposes the expanding danger of software patents and
look-and-feel copyrights.  More information on the LPF's views is
available at @uref{http://progfree.org/, the LPF home page}.

@node Real meaning of copyleft
@section What is the real legal meaning of the GNU copyleft?
@cindex Copyleft, real meaning of
@cindex GPL, real meaning of
@cindex General Public License, real meaning of
@cindex Discussion of the GPL

The real legal meaning of the GNU General Public License (copyleft) will
only be known if and when a judge rules on its validity and scope.
There has never been a copyright infringement case involving the GPL to
set any precedents.  Although legal actions have been brought against
companies for violating the terms of the GPL, so far all have been
settled out of court (in favor of the plaintiffs).  Please take any
discussion regarding this issue to the newsgroup
@uref{news:gnu.misc.discuss}, which was created to hold the extensive
flame wars on the subject.

RMS writes:

@quotation
The legal meaning of the GNU copyleft is less important than the spirit,
which is that Emacs is a free software project and that work pertaining
to Emacs should also be free software.  ``Free'' means that all users
have the freedom to study, share, change and improve Emacs.  To make
sure everyone has this freedom, pass along source code when you
distribute any version of Emacs or a related program, and give the
recipients the same freedom that you enjoyed.
@end quotation

@node Guidelines for newsgroup postings
@section  What are appropriate messages for the various Emacs newsgroups?
@cindex Newsgroups, appropriate messages for
@cindex GNU newsgroups, appropriate messages for
@cindex Usenet groups, appropriate messages for
@cindex Mailing lists, appropriate messages for
@cindex Posting messages to newsgroups

@cindex GNU mailing lists
The file @file{etc/MAILINGLISTS} describes the purpose of each GNU
mailing list (@pxref{Informational files for Emacs}).  For those lists
which are gatewayed with newsgroups, it lists both the newsgroup name
and the mailing list address.  The Emacs mailing lists are also
described at @uref{http://savannah.gnu.org/mail/?group=emacs, the Emacs
Savannah page}.

The newsgroup @uref{news:comp.emacs} is for discussion of Emacs programs
in general.  The newsgroup @uref{news:gnu.emacs.help} is specifically
for GNU Emacs.  It therefore makes no sense to cross-post to both
groups, since only one can be appropriate to any question.

Messages advocating ``non-free'' software are considered unacceptable on
any of the @code{gnu.*} newsgroups except for @uref{news:gnu.misc.discuss},
which was created to hold the extensive flame-wars on the subject.
``Non-free'' software includes any software for which the end user can't
freely modify the source code and exchange enhancements.  Be careful to
remove the @code{gnu.*} groups from the @samp{Newsgroups:} line when
posting a followup that recommends such software.

@uref{news:gnu.emacs.bug} is a place where bug reports appear, but avoid
posting bug reports to this newsgroup directly (@pxref{Reporting bugs}).

@node Newsgroup archives
@section Where can I get old postings to @uref{news:gnu.emacs.help} and other GNU groups?
@cindex Archived postings from @code{gnu.emacs.help}
@cindex Usenet archives for GNU groups
@cindex Old Usenet postings for GNU groups

The FSF has maintained archives of all of the GNU mailing lists for many
years, although there may be some unintentional gaps in coverage.  The
archive can be browsed over the web at
@uref{http://lists.gnu.org/archive/html/, the GNU mail archive}.  Raw
files can be downloaded from @uref{ftp://lists.gnu.org/}.

Web-based Usenet search services, such as
@uref{http://groups.google.com/groups/dir?q=gnu&, Google}, also
archive the @code{gnu.*} groups.

You can also read the archives of the @code{gnu.*} groups and post new
messages at @uref{http://gmane.org/, Gmane}.  Gmane is a service that
presents mailing lists as newsgroups (even those without a traditional
mail-to-news gateway).

@node Reporting bugs
@section Where should I report bugs and other problems with Emacs?
@cindex Bug reporting
@cindex Good bug reports
@cindex How to submit a bug report
@cindex Reporting bugs

The correct way to report Emacs bugs is to use the command
@kbd{M-x report-emacs-bug}.  It sets up a mail buffer with the
essential information and the correct e-mail address, which is
@email{bug-gnu-emacs@@gnu.org} for the released versions of Emacs.
Anything sent to @email{bug-gnu-emacs@@gnu.org} also appears in the
newsgroup @uref{news:gnu.emacs.bug}, but please use e-mail instead of
news to submit the bug report.  This ensures a reliable return address
so you can be contacted for further details.

Be sure to read the ``Bugs'' section of the Emacs manual before reporting
a bug!  The manual describes in detail how to submit a useful bug
report (@pxref{Bugs, , Reporting Bugs, emacs, The GNU Emacs Manual}).
(@xref{Emacs manual}, if you don't know how to read the manual.)

RMS says:

@quotation
Sending bug reports to @email{help-gnu-emacs@@gnu.org} (which has the
effect of posting on @uref{news:gnu.emacs.help}) is undesirable because
it takes the time of an unnecessarily large group of people, most of
whom are just users and have no idea how to fix these problem.
@email{bug-gnu-emacs@@gnu.org} reaches a much smaller group of people
who are more likely to know what to do and have expressed a wish to
receive more messages about Emacs than the others.
@end quotation

RMS says it is sometimes fine to post to @uref{news:gnu.emacs.help}:

@quotation
If you have reported a bug and you don't hear about a possible fix,
then after a suitable delay (such as a week) it is okay to post on
@code{gnu.emacs.help} asking if anyone can help you.
@end quotation

If you are unsure whether you have found a bug, consider the following
non-exhaustive list, courtesy of RMS:

@quotation
If Emacs crashes, that is a bug.  If Emacs gets compilation errors
while building, that is a bug.  If Emacs crashes while building, that
is a bug.  If Lisp code does not do what the documentation says it
does, that is a bug.
@end quotation

@node Unsubscribing from Emacs lists
@section  How do I unsubscribe from a mailing list?
@cindex Unsubscribing from GNU mailing lists
@cindex Removing yourself from GNU mailing lists

If you are receiving a GNU mailing list named @var{list}, you should be
able to unsubscribe from it by sending a request to the address
@email{@var{list}-request@@gnu.org}.  Mailing lists mails normally
contain information in either the message header
(@samp{List-Unsubscribe:}) or as a footer that tells you how to
unsubscribe.

@node Contacting the FSF
@section  How do I contact the FSF?
@cindex Contracting the FSF
@cindex Free Software Foundation, contacting

For up-to-date information, see
@uref{http://www.fsf.org/about/contact.html, the FSF contact web-page}.
You can send general correspondence to @email{info@@fsf.org}.

@cindex Ordering GNU software
For details on how to order items directly from the FSF, see the
@uref{http://shop.fsf.org/, FSF on-line store}.

@c ------------------------------------------------------------
@node Getting help
@chapter Getting help
@cindex Getting help

This chapter tells you how to get help with Emacs.

@menu
* Basic editing::
* Learning how to do something::
* Getting a printed manual::
* Emacs Lisp documentation::
* Installing Texinfo documentation::
* Printing a Texinfo file::
* Viewing Info files outside of Emacs::
* Informational files for Emacs::
* Help installing Emacs::
* Obtaining the FAQ::
@end menu

@node Basic editing
@section I'm just starting Emacs; how do I do basic editing?
@cindex Basic editing with Emacs
@cindex Beginning editing
@cindex Tutorial, invoking the
@cindex Self-paced tutorial, invoking the
@cindex Help system, entering the

Type @kbd{C-h t} to invoke the self-paced tutorial.  Just typing
@kbd{C-h} enters the help system.  Starting with Emacs 22, the tutorial
is available in many foreign languages such as French, German, Japanese,
Russian, etc.  Use @kbd{M-x help-with-tutorial-spec-language @key{RET}}
to choose your language and start the tutorial.

Your system administrator may have changed @kbd{C-h} to act like
@key{DEL} to deal with local keyboards.  You can use @kbd{M-x
help-for-help} instead to invoke help.  To discover what key (if any)
invokes help on your system, type @kbd{M-x where-is @key{RET}
help-for-help @key{RET}}.  This will print a comma-separated list of key
sequences in the echo area.  Ignore the last character in each key
sequence listed.  Each of the resulting key sequences (e.g. @key{F1} is
common) invokes help.

Emacs help works best if it is invoked by a single key whose value
should be stored in the variable @code{help-char}.

@node Learning how to do something
@section How do I find out how to do something in Emacs?
@cindex Help for Emacs
@cindex Learning to do something in Emacs
@cindex Reference card for Emacs
@cindex Overview of help systems

There are several methods for finding out how to do things in Emacs.

@itemize @bullet

@cindex Reading the Emacs manual
@item
The complete text of the Emacs manual is available via the Info
hypertext reader.  Type @kbd{C-h r} to display the manual in Info mode.
Typing @key{h} immediately after entering Info will provide a short
tutorial on how to use it.

@cindex Lookup a subject in a manual
@cindex Index search in a manual
@item
To quickly locate the section of the manual which discusses a certain
issue, or describes a command or a variable, type @kbd{C-h i m emacs
@key{RET} i @var{topic} @key{RET}}, where @var{topic} is the name of the
topic, the command, or the variable which you are looking for.  If this
does not land you on the right place in the manual, press @kbd{,}
(comma) repeatedly until you find what you need.  (The @kbd{i} and
@kbd{,} keys invoke the index-searching functions, which look for the
@var{topic} you type in all the indices of the Emacs manual.)

@cindex Apropos
@item
You can list all of the commands whose names contain a certain word
(actually which match a regular expression) using @kbd{C-h a} (@kbd{M-x
command-apropos}).

@cindex Command description in the manual
@item
The command @kbd{C-h F} (@code{Info-goto-emacs-command-node}) prompts
for the name of a command, and then attempts to find the section in the
Emacs manual where that command is described.

@cindex Finding commands and variables
@item
You can list all of the functions and variables whose names contain a
certain word using @kbd{M-x apropos}.

@item
You can list all of the functions and variables whose documentation
matches a regular expression or a string, using @kbd{M-x
apropos-documentation}.

@item
You can order a hardcopy of the manual from the FSF.  @xref{Getting a
printed manual}.

@cindex Reference cards, in other languages
@item
You can get a printed reference card listing commands and keys to
invoke them.  You can order one from the FSF for $2 (or 10 for $18),
or you can print your own from the @file{etc/refcards/refcard.tex} or
@file{etc/refcards/refcard.pdf} files in the Emacs distribution.
Beginning with version 21.1, the Emacs distribution comes with
translations of the reference card into several languages; look for
files named @file{etc/refcards/@var{lang}-refcard.*}, where @var{lang}
is a two-letter code of the language.  For example, the German version
of the reference card is in the files @file{etc/refcards/de-refcard.tex}
and @file{etc/refcards/de-refcard.pdf}.

@item
There are many other commands in Emacs for getting help and
information.  To get a list of these commands, type @samp{?} after
@kbd{C-h}.

@end itemize

@node Getting a printed manual
@section How do I get a printed copy of the Emacs manual?
@cindex Printed Emacs manual, obtaining
@cindex Manual, obtaining a printed or HTML copy of
@cindex Emacs manual, obtaining a printed or HTML copy of

You can order a printed copy of the Emacs manual from the FSF.  For
details see the @uref{http://shop.fsf.org/, FSF on-line store}.

The full Texinfo source for the manual also comes in the @file{doc/emacs}
directory of the Emacs distribution, if you're daring enough to try to
print out this several-hundred-page manual yourself (@pxref{Printing a Texinfo
file}).

If you absolutely have to print your own copy, and you don't have @TeX{},
you can get a PostScript or PDF (or HTML) version from

@uref{http://www.gnu.org/software/emacs/manual/}

@xref{Learning how to do something}, for how to view the manual from Emacs.

@node Emacs Lisp documentation
@section Where can I get documentation on Emacs Lisp?
@cindex Documentation on Emacs Lisp
@cindex Function documentation
@cindex Variable documentation
@cindex Emacs Lisp Reference Manual
@cindex Reference manual for Emacs Lisp

Within Emacs, you can type @kbd{C-h f} to get the documentation for a
function, @kbd{C-h v} for a variable.

For more information, the Emacs Lisp Reference Manual is available
in Info format (@pxref{Top, Emacs Lisp,, elisp, The
Emacs Lisp Reference Manual}).

You can also order a hardcopy of the manual from the FSF, for details
see the @uref{http://shop.fsf.org/, FSF on-line store}.  (This manual is
not always in print.)

An HTML version of the Emacs Lisp Reference Manual is available at

@uref{http://www.gnu.org/software/emacs/elisp-manual/elisp.html}

@node Installing Texinfo documentation
@section How do I install a piece of Texinfo documentation?
@cindex Texinfo documentation, installing
@cindex Installing Texinfo documentation
@cindex New Texinfo files, installing
@cindex Documentation, installing new Texinfo files
@cindex Info files, how to install

Emacs releases come with pre-built Info files, and the normal install
process places them in the correct location.  This is true for most
applications that provide Info files.  The following section is only
relevant if you want to install extra Info files by hand.

First, you must turn the Texinfo source files into Info files.  You may
do this using the stand-alone @file{makeinfo} program, available as part
of the Texinfo package at

@uref{http://www.gnu.org/software/texinfo/}

For information about the Texinfo format, read the Texinfo manual which
comes with the Texinfo package.  This manual also comes installed in
Info format, so you can read it from Emacs; type @kbd{C-h i m texinfo
@key{RET}}.

@c FIXME is this a complete alternative?
@c Probably not, given that we require makeinfo to build Emacs.
Alternatively, you could use the Emacs command @kbd{M-x
texinfo-format-buffer}, after visiting the Texinfo source file of the
manual you want to convert.

Neither @code{texinfo-format-buffer} nor @file{makeinfo} installs the
resulting Info files in Emacs's Info tree.  To install Info files,
perform these steps:

@enumerate
@item
Move the files to the @file{info} directory in the installed Emacs
distribution.  @xref{File-name conventions}, if you don't know where that
is.

@item
Run the @code{install-info} command, which is part of the Texinfo
distribution, to update the main Info directory menu, like this:

@example
 install-info --info-dir=@var{dir-path} @var{dir-path}/@var{file}
@end example

@noindent
where @var{dir-path} is the full path to the directory where you copied
the produced Info file(s), and @var{file} is the name of the Info file
you produced and want to install.

If you don't have the @code{install-info} command installed, you can
edit the file @file{info/dir} in the installed Emacs distribution, and
add a line for the top level node in the Info package that you are
installing.  Follow the examples already in this file.  The format is:

@example
* Topic: (relative-pathname).  Short description of topic.
@end example

@end enumerate

If you want to install Info files and you don't have the necessary
privileges, you have several options:

@itemize @bullet
@item
Info files don't actually need to be installed before being used.
You can use a prefix argument for the @code{info} command and specify
the name of the Info file in the minibuffer.  This goes to the node
named @samp{Top} in that file.  For example, to view a Info file named
@file{@var{info-file}} in your home directory, you can type this:

@example
@kbd{C-u C-h i ~/@var{info-file} @key{RET}}
@end example

Alternatively, you can feed a file name to the @code{Info-goto-node}
command (invoked by pressing @key{g} in Info mode) by typing the name
of the file in parentheses, like this:

@example
@kbd{C-h i g (~/@var{info-file}) @key{RET}}
@end example

@item
You can create your own Info directory.  You can tell Emacs where that
Info directory is by adding its pathname to the value of the variable
@code{Info-default-directory-list}.  For example, to use a private Info
directory which is a subdirectory of your home directory named @file{Info},
you could put this in your @file{.emacs} file:

@lisp
(add-to-list 'Info-default-directory-list "~/Info")
@end lisp

You will need a top-level Info file named @file{dir} in this directory
which has everything the system @file{dir} file has in it, except it
should list only entries for Info files in that directory.  You might
not need it if (fortuitously) all files in this directory were
referenced by other @file{dir} files.  The node lists from all
@file{dir} files in @code{Info-default-directory-list} are merged by the
Info system.

@end itemize

@node Printing a Texinfo file
@section How do I print a Texinfo file?
@cindex Printing a Texinfo file
@cindex Texinfo file, printing
@cindex Printing documentation

You can't get nicely printed output from Info files; you must still have
the original Texinfo source file for the manual you want to print.

Assuming you have @TeX{} installed on your system, follow these steps:

@enumerate

@item
Make sure the first line of the Texinfo file looks like this:

@example
\input texinfo
@end example

You may need to change @samp{texinfo} to the full pathname of the
@file{texinfo.tex} file, which comes with Emacs as
@file{doc/misc/texinfo.tex} (or copy or link it into the current directory).

@item
Type @kbd{texi2dvi @var{texinfo-source}}, where @var{texinfo-source} is
the name of the Texinfo source file for which you want to produce a
printed copy.  The @samp{texi2dvi} script is part of the GNU Texinfo
distribution.

Alternatively, @samp{texi2pdf} produces PDF files.

@item
Print the DVI file @file{@var{texinfo-source}.dvi} in the normal way for
printing DVI files at your site.  For example, if you have a PostScript
printer, run the @code{dvips} program to print the DVI file on that
printer.

@end enumerate

To get more general instructions, retrieve the latest Texinfo package
(@pxref{Installing Texinfo documentation}).

@node Viewing Info files outside of Emacs
@section Can I view Info files without using Emacs?
@cindex Viewing Info files
@cindex Info file viewers
@cindex Alternative Info file viewers

Yes.  Here are some alternative programs:

@itemize @bullet

@item
@code{info}, a stand-alone version of the Info program, comes as part of
the Texinfo package.  @xref{Installing Texinfo documentation}, for
details.

@item
Tkinfo, an Info viewer that runs under X Window system and uses Tcl/Tk.
You can get Tkinfo at
@uref{http://math-www.uni-paderborn.de/~axel/tkinfo/}.

@end itemize

@node Informational files for Emacs
@section What informational files are available for Emacs?
@cindex Informational files included with Emacs
@cindex Files included with Emacs
@cindex @file{COPYING}, description of file
@cindex @file{DISTRIB}, description of file
@cindex @file{GNU}, description of file
@cindex @file{INTERVIEW}, description of file
@cindex @file{MACHINES}, description of file
@cindex @file{MAILINGLISTS}, description of file
@cindex @file{NEWS}, description of file

This isn't a frequently asked question, but it should be!  A variety of
informational files about Emacs and relevant aspects of the GNU project
are available for you to read.

The following files (and others) are available in the @file{etc}
directory of the Emacs distribution (see @ref{File-name conventions}, if
you're not sure where that is).  Many of these files are available via
the Emacs @samp{Help} menu, or by typing @kbd{C-h ?} (@kbd{M-x
help-for-help}).

@table @file

@item COPYING
GNU General Public License

@item DISTRIB
Emacs Availability Information

@item GNU
The GNU Manifesto

@item INTERVIEW
Richard Stallman discusses his public-domain UNIX-compatible software
system with BYTE editors

@item MACHINES
Status of Emacs on Various Machines and Systems

@item MAILINGLISTS
GNU Project Electronic Mailing Lists

@item NEWS
Emacs news, a history of recent user-visible changes

@end table

More GNU information, including back issues of the @cite{GNU's
Bulletin}, are at

@uref{http://www.gnu.org/bulletins/bulletins.html} and

@uref{http://www.cs.pdx.edu/~trent/gnu/gnu.html}

@node Help installing Emacs
@section Where can I get help in installing Emacs?
@cindex Installation help
@cindex Help installing Emacs

@xref{Installing Emacs}, for some basic installation hints, and see
@ref{Problems building Emacs}, if you have problems with the installation.

@uref{http://www.fsf.org/resources/service/, The GNU Service directory}
lists companies and individuals willing to sell you help in installing
or using Emacs and other GNU software.

@node Obtaining the FAQ
@section Where can I get the latest version of this FAQ?
@cindex FAQ, obtaining the
@cindex Latest FAQ version, obtaining the

The Emacs FAQ is distributed with Emacs in Info format.  You can read it
by selecting the @samp{Emacs FAQ} option from the @samp{Help} menu of
the Emacs menu bar at the top of any Emacs frame, or by typing @kbd{C-h
C-f} (@kbd{M-x view-emacs-FAQ}).  The very latest version is available
in the Emacs development repository (@pxref{Latest version of Emacs}).

@c ------------------------------------------------------------
@node Status of Emacs
@chapter Status of Emacs
@cindex Status of Emacs

This chapter gives you basic information about Emacs, including the
status of its latest version.

@menu
* Origin of the term Emacs::
* Latest version of Emacs::
* New in Emacs 23::
* New in Emacs 22::
* New in Emacs 21::
* New in Emacs 20::
@end menu

@node Origin of the term Emacs
@section Where does the name ``Emacs'' come from?
@cindex Origin of the term ``Emacs''
@cindex Emacs name origin
@cindex TECO
@cindex Original version of Emacs

Emacs originally was an acronym for Editor MACroS.  RMS says he ``picked
the name Emacs because @key{E} was not in use as an abbreviation on ITS at
the time.''  The first Emacs was a set of macros written in 1976 at MIT
by RMS for the editor TECO (Text Editor and COrrector, originally Tape
Editor and COrrector) under ITS (the Incompatible Timesharing System) on
a PDP-10.  RMS had already extended TECO with a ``real-time''
full-screen mode with reprogrammable keys.  Emacs was started by
@email{gls@@east.sun.com, Guy Steele} as a project to unify the many
divergent TECO command sets and key bindings at MIT, and completed by
RMS.

Many people have said that TECO code looks a lot like line noise; you
can read more at @uref{news:alt.lang.teco}.  Someone has written a TECO
implementation in Emacs Lisp (to find it, see @ref{Packages that do not
come with Emacs}); it would be an interesting project to run the
original TECO Emacs inside of Emacs.

@cindex Why Emacs?
For some not-so-serious alternative reasons for Emacs to have that
name, check out the file @file{etc/JOKES} (@pxref{File-name
conventions}).

@node Latest version of Emacs
@section What is the latest version of Emacs?
@cindex Version, latest
@cindex Latest version of Emacs
@cindex Development, Emacs
@cindex Repository, Emacs
@cindex Bazaar repository, Emacs

Emacs @value{EMACSVER} is the current version as of this writing.  A version
number with two components (e.g. @samp{22.1}) indicates a released
version; three components indicate a development
version (e.g. @samp{23.0.50} is what will eventually become @samp{23.1}).

Emacs is under active development, hosted at
@uref{http://savannah.gnu.org/projects/emacs/, Savannah}.  The source
code can be retrieved anonymously following the
@uref{http://savannah.gnu.org/bzr/?group=emacs, instructions}.
The repository is GNU Bazaar.

Because Emacs undergoes many changes before a release, the version
number of a development version is not especially meaningful.  It is
better to refer to the date on which the sources were retrieved from the
development repository.  The development version is usually quite robust
for every-day use, but if stability is more important to you than the
latest features, you may want to stick to the releases.

The following sections list some of the major new features in the last
few Emacs releases.  For full details of the changes in any version of
Emacs, type @kbd{C-h C-n} (@kbd{M-x view-emacs-news}).  As of Emacs 22,
you can give this command a prefix argument to read about which features
were new in older versions.

@node New in Emacs 23
@section What is different about Emacs 23?
@cindex Differences between Emacs 22 and Emacs 23
@cindex Emacs 23, new features in
@cindex Recently introduced features
@cindex Default features

@itemize

@cindex Anti-aliased fonts
@cindex Freetype fonts
@item
Emacs has a new font code that can use multiple font backends,
including freetype and fontconfig.  Emacs can use the Xft library for
anti-aliasing, and the otf and m17n libraries for complex text layout and
text shaping.

@cindex Unicode
@cindex Character sets
@item
The Emacs character set is now a superset of Unicode.  Several new
language environments have been added.

@cindex Multi-tty support
@cindex X and tty displays
@item
Emacs now supports using both X displays and ttys in the same session
(@samp{multi-tty}).

@cindex Daemon mode
@item
Emacs can be started as a daemon in the background.

@cindex NeXTstep port
@cindex GNUstep port
@cindex Mac OS X Cocoa
@item
There is a new NeXTstep port of Emacs.  This supports GNUstep and Mac OS
X (via the Cocoa libraries).  The Carbon port of Emacs, which supported
Mac OS X in Emacs 22, has been removed.

@cindex Directory-local variables
@item
Directory-local variables can now be defined, in a similar manner to
file-local variables.

@item
Transient Mark mode (@pxref{Highlighting a region}) is on by default.

@end itemize

@noindent
Other changes include: support for serial port access; D-Bus bindings; a
new Visual Line mode for line-motion; improved completion; a new mode
(@samp{DocView}) for viewing of PDF, PostScript, and DVI documents; nXML
mode (for editing XML documents) is included; VC has been updated for
newer version control systems; etc.  As always, consult the @file{NEWS}
file for more information.


@node New in Emacs 22
@section What is different about Emacs 22?
@cindex Differences between Emacs 21 and Emacs 22
@cindex Emacs 22, new features in

@itemize
@cindex GTK+ Toolkit
@cindex Drag-and-drop
@item
Emacs can be built with GTK+ widgets, and supports drag-and-drop
operation on X.

@cindex Supported systems
@item
Emacs 22 features support for GNU/Linux systems on S390 and x86-64
machines, as well as support for the Mac OS X and Cygwin operating
systems.

@item
The native MS-Windows, and Mac OS X builds include full support
for images, toolbar, and tooltips.

@item
Font Lock mode, Auto Compression mode, and File Name Shadow Mode are
enabled by default.

@item
The maximum size of buffers is increased: on 32-bit machines, it is
256 MBytes for Emacs 23.1, and 512 MBytes for Emacs 23.2 and above.

@item
Links can be followed with @kbd{mouse-1}, in addition to @kbd{mouse-2}.

@cindex Mouse wheel
@item
Mouse wheel support is enabled by default.

@item
Window fringes are customizable.

@item
The mode line of the selected window is now highlighted.

@item
The minibuffer prompt is displayed in a distinct face.

@item
Abbrev definitions are read automatically at startup.

@item
Grep mode is separate from Compilation mode and has many new options and
commands specific to grep.

@item
The original Emacs macro system has been replaced by the new Kmacro
package, which provides many new commands and features and a simple
interface that uses the function keys F3 and F4.  Macros are stored in a
macro ring, and can be debugged and edited interactively.

@item
The Grand Unified Debugger (GUD) can be used with a full graphical user
interface to GDB; this provides many features found in traditional
development environments, making it easy to manipulate breakpoints, add
watch points, display the call stack, etc.  Breakpoints are visually
indicated in the source buffer.

@item
@cindex New modes
Many new modes and packages have been included in Emacs, such as Calc,
TRAMP, URL, IDO, CUA, ERC, rcirc, Table, Image-Dired, SES, Ruler, Org,
PGG, Flymake, Password, Printing, Reveal, wdired, t-mouse, longlines,
savehist, Conf mode, Python mode, DNS mode, etc.

@cindex Multilingual Environment
@item
Leim is now part of Emacs.  Unicode support has been much improved, and
the following input methods have been added: belarusian, bulgarian-bds,
bulgarian-phonetic, chinese-sisheng, croatian, dutch, georgian,
latin-alt-postfix, latin-postfix, latin-prefix, latvian-keyboard,
lithuanian-numeric, lithuanian-keyboard, malayalam-inscript, rfc1345,
russian-computer, sgml, slovenian, tamil-inscript, ucs,
ukrainian-computer, vietnamese-telex, and welsh.

The following language environments have also been added: Belarusian,
Bulgarian, Chinese-EUC-TW, Croatian, French, Georgian, Italian, Latin-6,
Latin-7, Latvian, Lithuanian, Malayalam, Russian, Slovenian, Swedish,
Tajik, Tamil, UTF-8, Ukrainian, Welsh, and Windows-1255.

@cindex Documentation
@cindex Emacs Lisp Manual
@item
In addition, Emacs 22 now includes the Emacs Lisp Reference Manual
(@pxref{Emacs Lisp documentation}) and the Emacs Lisp Intro.
@end itemize


@node New in Emacs 21
@section What is different about Emacs 21?
@cindex Differences between Emacs 20 and Emacs 21
@cindex Emacs 21, new features in

@cindex Variable-size fonts
@cindex Toolbar support
Emacs 21 features a thorough rewrite of the display engine.  The new
display engine supports variable-size fonts, images, and can play sounds
on platforms which support that.  As a result, the visual appearance of
Emacs, when it runs on a windowed display, is much more reminiscent of
modern GUI programs, and includes 3D widgets (used for the mode line and
the scroll bars), a configurable and extensible toolbar, tooltips
(a.k.a.@: balloon help), and other niceties.

@cindex Colors on text-only terminals
@cindex TTY colors
In addition, Emacs 21 supports faces on text-only terminals.  This means
that you can now have colors when you run Emacs on a GNU/Linux console
and on @code{xterm} with @kbd{emacs -nw}.


@node New in Emacs 20
@section What is different about Emacs 20?
@cindex Differences between Emacs 19 and Emacs 20
@cindex Emacs 20, new features in

The differences between Emacs versions 18 and 19 were rather dramatic;
the introduction of frames, faces, and colors on windowing systems was
obvious to even the most casual user.

There are differences between Emacs versions 19 and 20 as well, but many
are more subtle or harder to find.  Among the changes are the inclusion
of MULE code for languages that use non-Latin characters and for mixing
several languages in the same document; the ``Customize'' facility for
modifying variables without having to use Lisp; and automatic conversion
of files from Macintosh, Microsoft, and Unix platforms.

@c ------------------------------------------------------------
@node Common requests
@chapter Common requests
@cindex Common requests

@menu
* Setting up a customization file::
* Using Customize::
* Colors on a TTY::
* Debugging a customization file::
* Displaying the current line or column::
* Displaying the current file name in the titlebar::
* Turning on abbrevs by default::
* Associating modes with files::
* Highlighting a region::
* Replacing highlighted text::
* Controlling case sensitivity::
* Working with unprintable characters::
* Searching for/replacing newlines::
* Yanking text in isearch::
* Wrapping words automatically::
* Turning on auto-fill by default::
* Changing load-path::
* Using an already running Emacs process::
* Compiler error messages::
* Indenting switch statements::
* Customizing C and C++ indentation::
* Horizontal scrolling::
* Overwrite mode::
* Turning off beeping::
* Turning the volume down::
* Automatic indentation::
* Matching parentheses::
* Hiding #ifdef lines::
* Repeating commands::
* Valid X resources::
* Evaluating Emacs Lisp code::
* Changing the length of a Tab::
* Inserting text at the beginning of each line::
* Forcing the cursor to remain in the same column::
* Forcing Emacs to iconify itself::
* Using regular expressions::
* Replacing text across multiple files::
* Documentation for etags::
* Disabling backups::
* Disabling auto-save-mode::
* Going to a line by number::
* Modifying pull-down menus::
* Deleting menus and menu options::
* Turning on syntax highlighting::
* Scrolling only one line::
* Editing MS-DOS files::
* Filling paragraphs with a single space::
* Escape sequences in shell output::
* Fullscreen mode on MS-Windows::
@end menu

@node Setting up a customization file
@section How do I set up a @file{.emacs} file properly?
@cindex @file{.emacs} file, setting up
@cindex @file{.emacs} file, locating
@cindex Init file, setting up
@cindex Customization file, setting up

@inforef{Init File, Init File, emacs}.

In general, new Emacs users should not be provided with @file{.emacs}
files, because this can cause confusing non-standard behavior.  Then
they send questions to @email{help-gnu-emacs@@gnu.org} asking why Emacs
isn't behaving as documented.

Emacs includes the Customize facility (@pxref{Using Customize}).  This
allows users who are unfamiliar with Emacs Lisp to modify their
@file{.emacs} files in a relatively straightforward way, using menus
rather than Lisp code.

While Customize might indeed make it easier to configure Emacs,
consider taking a bit of time to learn Emacs Lisp and modifying your
@file{.emacs} directly.  Simple configuration options are described
rather completely in @inforef{Init File, Init File, emacs}, for users
interested in performing frequently requested, basic tasks.

Sometimes users are unsure as to where their @file{.emacs} file should
be found.  Visiting the file as @file{~/.emacs} from Emacs will find
the correct file.

@node Using Customize
@section How do I start using Customize?
@cindex Customize groups
@cindex Customizing variables
@cindex Customizing faces

The main Customize entry point is @kbd{M-x customize @key{RET}}.  This
command takes you to a buffer listing all the available Customize
groups.  From there, you can access all customizable options and faces,
change their values, and save your changes to your init file.
@inforef{Easy Customization, Easy Customization, emacs}.

If you know the name of the group in advance (e.g. ``shell''), use
@kbd{M-x customize-group @key{RET}}.

If you wish to customize a single option, use @kbd{M-x customize-option
@key{RET}}.  This command prompts you for the name of the option to
customize, with completion.

@node Colors on a TTY
@section How do I get colors and syntax highlighting on a TTY?
@cindex Colors on a TTY
@cindex Syntax highlighting on a TTY
@cindex Console, colors

In Emacs 21.1 and later, colors and faces are supported in non-windowed mode,
i.e.@: on Unix and GNU/Linux text-only terminals and consoles, and when
invoked as @samp{emacs -nw} on X, and MS-Windows.  (Colors and faces were
supported in the MS-DOS port since Emacs 19.29.)  Emacs automatically
detects color support at startup and uses it if available.  If you think
that your terminal supports colors, but Emacs won't use them, check the
@code{termcap} entry for your display type for color-related
capabilities.

The command @kbd{M-x list-colors-display} pops up a window which
exhibits all the colors Emacs knows about on the current display.

Syntax highlighting is on by default since version 22.1.

@node Debugging a customization file
@section How do I debug a @file{.emacs} file?
@cindex Debugging @file{.emacs} file
@cindex @file{.emacs} debugging
@cindex Init file debugging
@cindex @samp{-debug-init} option

Start Emacs with the @samp{-debug-init} command-line option.  This
enables the Emacs Lisp debugger before evaluating your @file{.emacs}
file, and places you in the debugger if something goes wrong.  The top
line in the @file{trace-back} buffer will be the error message, and the
second or third line of that buffer will display the Lisp code from your
@file{.emacs} file that caused the problem.

You can also evaluate an individual function or argument to a function
in your @file{.emacs} file by moving the cursor to the end of the
function or argument and typing @kbd{C-x C-e} (@kbd{M-x
eval-last-sexp}).

Use @kbd{C-h v} (@kbd{M-x describe-variable}) to check the value of
variables which you are trying to set or use.

@node Displaying the current line or column
@section How do I make Emacs display the current line (or column) number?
@cindex @code{line-number-mode}
@cindex Displaying the current line or column
@cindex Line number, displaying the current
@cindex Column, displaying the current
@cindex @code{mode-line-format}

By default, Emacs displays the current line number of the point in the
mode line.  You can toggle this feature off or on with the command
@kbd{M-x line-number-mode}, or by setting the variable
@code{line-number-mode}.  Note that Emacs will not display the line
number if the buffer's size in bytes is larger than the value of the
variable @code{line-number-display-limit}.

You can similarly display the current column with
@kbd{M-x column-number-mode}, or by putting the form

@lisp
(setq column-number-mode t)
@end lisp

@noindent
in your @file{.emacs} file.  This feature is off by default.

The @code{"%c"} format specifier in the variable @code{mode-line-format}
will insert the current column's value into the mode line.  See the
documentation for @code{mode-line-format} (using @kbd{C-h v
mode-line-format @key{RET}}) for more information on how to set and use
this variable.

@cindex Set number capability in @code{vi} emulators
The @samp{linum} package (distributed with Emacs since version 23.1)
displays line numbers in the left margin, like the ``set number''
capability of @code{vi}.  The packages @samp{setnu} and
@samp{wb-line-number} (not distributed with Emacs) also implement this
feature.

@node Displaying the current file name in the titlebar
@section How can I modify the titlebar to contain the current file name?
@cindex Titlebar, displaying the current file name in
@cindex File name, displaying in the titlebar
@cindex @code{frame-title-format}

The contents of an Emacs frame's titlebar is controlled by the variable
@code{frame-title-format}, which has the same structure as the variable
@code{mode-line-format}.  (Use @kbd{C-h v} or @kbd{M-x
describe-variable} to get information about one or both of these
variables.)

By default, the titlebar for a frame does contain the name of the buffer
currently being visited, except if there is a single frame.  In such a
case, the titlebar contains Emacs invocation name and the name of the
machine at which Emacs was invoked.  This is done by setting
@code{frame-title-format} to the default value of

@lisp
(multiple-frames "%b" ("" invocation-name "@@" system-name))
@end lisp

To modify the behavior such that frame titlebars contain the buffer's
name regardless of the number of existing frames, include the following
in your @file{.emacs}:

@lisp
(setq frame-title-format "%b")
@end lisp

@node Turning on abbrevs by default
@section How do I turn on abbrevs by default just in mode @var{mymode}?
@cindex Abbrevs, turning on by default

Abbrev mode expands abbreviations as you type them.  To turn it on in a
specific buffer, use @kbd{M-x abbrev-mode}.  To turn it on in every
buffer by default, put this in your @file{.emacs} file:

@lisp
(setq-default abbrev-mode t)
@end lisp

@noindent To turn it on in a specific mode, use:

@lisp
(add-hook '@var{mymode}-mode-hook
          (lambda ()
           (setq abbrev-mode t)))
@end lisp

@noindent If your Emacs version is older then 22.1, you will also need to use:

@lisp
(condition-case ()
   (quietly-read-abbrev-file)
  (file-error nil))
@end lisp

@node Associating modes with files
@section How do I make Emacs use a certain major mode for certain files?
@cindex Associating modes with files
@cindex File extensions and modes
@cindex @code{auto-mode-alist}, modifying
@cindex Modes, associating with file extensions

If you want to use a certain mode @var{foo} for all files whose names end
with the extension @file{.@var{bar}}, this will do it for you:

@lisp
(add-to-list 'auto-mode-alist '("\\.@var{bar}\\'" . @var{foo}-mode))
@end lisp

Alternatively, put this somewhere in the first line of any file you want to
edit in the mode @var{foo} (in the second line, if the first line begins
with @samp{#!}):

@example
-*- @var{foo} -*-
@end example

@cindex Major mode for shell scripts
The variable @code{interpreter-mode-alist} specifies which mode to use
when loading an interpreted script (e.g. shell, python, etc.).  Emacs
determines which interpreter you're using by examining the first line of
the script.  Use @kbd{C-h v} (or @kbd{M-x describe-variable}) on
@code{interpreter-mode-alist} to learn more.

@node Highlighting a region
@section How can I highlight a region of text in Emacs?
@cindex Highlighting text
@cindex Text, highlighting
@cindex @code{transient-mark-mode}
@cindex Region, highlighting a

You can cause the region to be highlighted when the mark is active by
including

@lisp
(transient-mark-mode 1)
@end lisp

@noindent
in your @file{.emacs} file.  Since Emacs 23.1, this feature is on by default.

@node Replacing highlighted text
@section How can I replace highlighted text with what I type?
@cindex @code{delete-selection-mode}
@cindex Replacing highlighted text
@cindex Highlighting and replacing text

Use @code{delete-selection-mode}, which you can start automatically by
placing the following Lisp form in your @file{.emacs} file:

@lisp
(delete-selection-mode 1)
@end lisp

According to the documentation string for @code{delete-selection-mode}
(which you can read using @kbd{M-x describe-function @key{RET}
delete-selection-mode @key{RET}}):

@quotation
When Delete Selection mode is enabled, Transient Mark mode is also
enabled and typed text replaces the selection if the selection is
active.  Otherwise, typed text is just inserted at point regardless of
any selection.
@end quotation

This mode also allows you to delete (not kill) the highlighted region by
pressing @key{DEL}.

@node Controlling case sensitivity
@section How do I control Emacs's case-sensitivity when searching/replacing?
@cindex @code{case-fold-search}
@cindex Case sensitivity of searches
@cindex Searching without case sensitivity
@cindex Ignoring case in searches

@c FIXME
The value of the variable @code{case-fold-search} determines whether
searches are case sensitive:

@lisp
(setq case-fold-search nil) ; make searches case sensitive
(setq case-fold-search t)   ; make searches case insensitive
@end lisp

@cindex Case sensitivity in replacements
@cindex Replacing, and case sensitivity
@cindex @code{case-replace}
Similarly, for replacing, the variable @code{case-replace} determines
whether replacements preserve case.

You can also toggle case sensitivity at will in isearch with @kbd{M-c}.

To change the case sensitivity just for one major mode, use the major
mode's hook.  For example:

@lisp
(add-hook '@var{foo}-mode-hook
          (lambda ()
           (setq case-fold-search nil)))
@end lisp

@node Working with unprintable characters
@section How do I search for, delete, or replace unprintable (eight-bit or control) characters?
@cindex Unprintable characters, working with
@cindex Working with unprintable characters
@cindex Control characters, working with
@cindex Eight-bit characters, working with
@cindex Searching for unprintable characters
@cindex Regexps and unprintable characters

To search for a single character that appears in the buffer as, for
example, @samp{\237}, you can type @kbd{C-s C-q 2 3 7}.
Searching for @strong{all} unprintable characters is best done with a
regular expression (@dfn{regexp}) search.  The easiest regexp to use for
the unprintable chars is the complement of the regexp for the printable
chars.

@itemize @bullet

@item
Regexp for the printable chars: @samp{[\t\n\r\f -~]}

@item
Regexp for the unprintable chars: @samp{[^\t\n\r\f -~]}

@end itemize

To type these special characters in an interactive argument to
@code{isearch-forward-regexp} or @code{re-search-forward}, you need to
use @kbd{C-q}.  (@samp{\t}, @samp{\n}, @samp{\r}, and @samp{\f} stand
respectively for @key{TAB}, @key{LFD}, @key{RET}, and @kbd{C-l}.)  So,
to search for unprintable characters using @code{re-search-forward}:

@kbd{M-x re-search-forward @key{RET} [^ @key{TAB} C-q @key{LFD} C-q @key{RET} C-q C-l @key{SPC} -~] @key{RET}}

Using @code{isearch-forward-regexp}:

@kbd{C-M-s [^ @key{TAB} @key{LFD} C-q @key{RET} C-q C-l @key{SPC} -~]}

To delete all unprintable characters, simply use replace-regexp:

@kbd{M-x replace-regexp @key{RET} [^ @key{TAB} C-q @key{LFD} C-q @key{RET} C-q C-l @key{SPC} -~] @key{RET} @key{RET}}

Replacing is similar to the above.  To replace all unprintable
characters with a colon, use:

M-x replace-regexp @key{RET} [^ @key{TAB} C-q @key{LFD} C-q @key{RET} C-q C-l @key{SPC} -~] @key{RET} : @key{RET}

@node Searching for/replacing newlines
@section How do I input a newline character in isearch or query-replace?
@cindex Searching for newlines
@cindex Replacing newlines

Use @kbd{C-q C-j}.  For more information, see @inforef{Special Isearch,
Special Input for Incremental Search, emacs}.


@node Yanking text in isearch
@section How do I copy text from the kill ring into the search string?
@cindex Yanking text into the search string
@cindex isearch yanking

Use @kbd{M-y}.  @inforef{Isearch Yank, Isearch Yanking, emacs}.

@node Wrapping words automatically
@section How do I make Emacs wrap words for me?
@cindex Wrapping word automatically
@cindex Wrapping lines
@cindex Line wrap
@cindex @code{auto-fill-mode}, introduction to
@cindex Maximum line width, default value
@cindex @code{fill-column}, default value

Use @code{auto-fill-mode}, activated by typing @kbd{M-x auto-fill-mode}.
The default maximum line width is 70, determined by the variable
@code{fill-column}.  To learn how to turn this on automatically, see
@ref{Turning on auto-fill by default}.

@node Turning on auto-fill by default
@section How do I turn on @code{auto-fill-mode} by default?
@cindex @code{auto-fill-mode}, activating automatically
@cindex Filling automatically
@cindex Automatic entry to @code{auto-fill-mode}

To turn on @code{auto-fill-mode} just once for one buffer, use @kbd{M-x
auto-fill-mode}.

To turn it on for every buffer in a certain mode, you must use the hook
for that mode.  For example, to turn on @code{auto-fill} mode for all
text buffers, including the following in your @file{.emacs} file:

@lisp
(add-hook 'text-mode-hook 'turn-on-auto-fill)
@end lisp

If you want @code{auto-fill} mode on in all major modes, do this:

@lisp
(setq-default auto-fill-function 'do-auto-fill)
@end lisp

@node Changing load-path
@section How do I change @code{load-path}?
@cindex @code{load-path}, modifying
@cindex Modifying @code{load-path}
@cindex Adding to @code{load-path}

In general, you should only add to the @code{load-path}.  You can add
directory @var{/dir/subdir} to the load path like this:

@lisp
(add-to-list 'load-path "/dir/subdir/")
@end lisp

To do this relative to your home directory:

@lisp
(add-to-list 'load-path "~/mysubdir/")
@end lisp

@node Using an already running Emacs process
@section How do I use an already running Emacs from another window?
@cindex @code{emacsclient}
@cindex Emacs server functions
@cindex Using an existing Emacs process

@code{emacsclient}, which comes with Emacs, is for editing a file using
an already running Emacs rather than starting up a new Emacs.  It does
this by sending a request to the already running Emacs, which must be
expecting the request.

@itemize @bullet

@item
Setup:

Emacs must have executed the @code{server-start} function for
@samp{emacsclient} to work.  This can be done either by a command line
option:

@example
emacs -f server-start
@end example

or by invoking @code{server-start} from @file{.emacs}:

@lisp
(if (@var{some conditions are met}) (server-start))
@end lisp

When this is done, Emacs creates a Unix domain socket named
@file{server} in @file{/tmp/emacs@var{userid}}. See
@code{server-socket-dir}.

To get your news reader, mail reader, etc., to invoke
@samp{emacsclient}, try setting the environment variable @code{EDITOR}
(or sometimes @code{VISUAL}) to the value @samp{emacsclient}.  You may
have to specify the full pathname of the @samp{emacsclient} program
instead.  Examples:

@example
# csh commands:
setenv EDITOR emacsclient

# using full pathname
setenv EDITOR /usr/local/emacs/etc/emacsclient

# sh command:
EDITOR=emacsclient ; export EDITOR
@end example

@item
Normal use:

When @samp{emacsclient} is run, it connects to the socket and passes its
command line options to Emacs, which at the next opportunity will visit
the files specified.  (Line numbers can be specified just like with
Emacs.)  The user will have to switch to the Emacs window by hand.  When
the user is done editing a file, the user can type @kbd{C-x #} (or
@kbd{M-x server-edit}) to indicate this.  If there is another buffer
requested by @code{emacsclient}, Emacs will switch to it; otherwise
@code{emacsclient} will exit, signaling the calling program to continue.

@cindex @code{gnuserv}
There is an alternative version of @samp{emacsclient} called
@samp{gnuserv}, written by @email{ange@@hplb.hpl.hp.com, Andy Norman}
(@pxref{Packages that do not come with Emacs}).  @samp{gnuserv} uses
Internet domain sockets, so it can work across most network connections.

The most recent @samp{gnuserv} package is available at

@uref{http://meltin.net/hacks/emacs/}

@end itemize

@node Compiler error messages
@section How do I make Emacs recognize my compiler's funny error messages?
@cindex Compiler error messages, recognizing
@cindex Recognizing non-standard compiler errors
@cindex Regexps for recognizing compiler errors
@cindex Errors, recognizing compiler

Customize the @code{compilation-error-regexp-alist} variable.

@node Indenting switch statements
@section How do I change the indentation for @code{switch}?
@cindex @code{switch}, indenting
@cindex Indenting of @code{switch}

Many people want to indent their @code{switch} statements like this:

@example
f()
@{
  switch(x) @{
    case A:
      x1;
      break;
    case B:
      x2;
      break;
    default:
      x3;
  @}
@}
@end example

@noindent To achieve this, add the following line to your @file{.emacs}:

@lisp
(c-set-offset 'case-label '+)
@end lisp

@node Customizing C and C++ indentation
@section How to customize indentation in C, C@t{++}, and Java buffers?
@cindex Indentation, how to customize
@cindex Customize indentation

The Emacs @code{cc-mode} features an interactive procedure for
customizing the indentation style, which is fully explained in the
@cite{CC Mode} manual that is part of the Emacs distribution, see
@ref{Customizing Indentation, , Customization Indentation, ccmode,
The CC Mode Manual}.  Here's a short summary of the procedure:

@enumerate
@item
Go to the beginning of the first line where you don't like the
indentation and type @kbd{C-c C-o}.  Emacs will prompt you for the
syntactic symbol; type @key{RET} to accept the default it suggests.

@item
Emacs now prompts for the offset of this syntactic symbol, showing the
default (the current definition) inside parentheses.  You can choose
one of these:

@table @code
@item 0
No extra indentation.
@item +
Indent one basic offset.
@item -
Outdent one basic offset.
@item ++
Indent two basic offsets
@item --
Outdent two basic offsets.
@item *
Indent half basic offset.
@item /
Outdent half basic offset.
@end table

@item
After choosing one of these symbols, type @kbd{C-c C-q} to reindent
the line or the block according to what you just specified.

@item
If you don't like the result, go back to step 1.  Otherwise, add the
following line to your @file{.emacs}:

@lisp
(c-set-offset '@var{syntactic-symbol} @var{offset})
@end lisp

@noindent
where @var{syntactic-symbol} is the name Emacs shows in the minibuffer
when you type @kbd{C-c C-o} at the beginning of the line, and
@var{offset} is one of the indentation symbols listed above (@code{+},
@code{/}, @code{0}, etc.) that you've chosen during the interactive
procedure.

@item
Go to the next line whose indentation is not to your liking and repeat
the process there.
@end enumerate

It is recommended to put all the resulting @code{(c-set-offset ...)}
customizations inside a C mode hook, like this:

@lisp
(defun my-c-mode-hook ()
  (c-set-offset ...)
  (c-set-offset ...))
(add-hook 'c-mode-hook 'my-c-mode-hook)
@end lisp

@noindent
Using @code{c-mode-hook} avoids the need to put a @w{@code{(require
'cc-mode)}} into your @file{.emacs} file, because @code{c-set-offset}
might be unavailable when @code{cc-mode} is not loaded.

Note that @code{c-mode-hook} runs for C source files only; use
@code{c++-mode-hook} for C@t{++} sources, @code{java-mode-hook} for
Java sources, etc.  If you want the same customizations to be in
effect in @emph{all} languages supported by @code{cc-mode}, use
@code{c-mode-common-hook}.

@node Horizontal scrolling
@section How can I make Emacs automatically scroll horizontally?
@cindex @code{hscroll-mode}
@cindex Horizontal scrolling
@cindex Scrolling horizontally

In Emacs 21 and later, this is on by default: if the variable
@code{truncate-lines} is non-@code{nil} in the current buffer, Emacs
automatically scrolls the display horizontally when point moves off the
left or right edge of the window.

Note that this is overridden by the variable
@code{truncate-partial-width-windows} if that variable is non-nil
and the current buffer is not full-frame width.

In Emacs 20, use @code{hscroll-mode}.

@node Overwrite mode
@section How do I make Emacs ``typeover'' or ``overwrite'' instead of inserting?
@cindex @key{Insert}
@cindex @code{overwrite-mode}
@cindex Overwriting existing text
@cindex Toggling @code{overwrite-mode}

@kbd{M-x overwrite-mode} (a minor mode).  This toggles
@code{overwrite-mode} on and off, so exiting from @code{overwrite-mode}
is as easy as another @kbd{M-x overwrite-mode}.

On some systems, @key{Insert} toggles @code{overwrite-mode} on and off.

@node Turning off beeping
@section How do I stop Emacs from beeping on a terminal?
@cindex Beeping, turning off
@cindex Visible bell
@cindex Bell, visible

@email{martin@@cc.gatech.edu, Martin R. Frank} writes:

Tell Emacs to use the @dfn{visible bell} instead of the audible bell,
and set the visible bell to nothing.

That is, put the following in your @code{TERMCAP} environment variable
(assuming you have one):

@example
... :vb=: ...
@end example

And evaluate the following Lisp form:

@example
(setq visible-bell t)
@end example

@node Turning the volume down
@section How do I turn down the bell volume in Emacs running under X?
@cindex Bell, volume of
@cindex Volume of bell

On X Window system, you can adjust the bell volume and duration for all
programs with the shell command @code{xset}.

Invoking @code{xset} without any arguments produces some basic
information, including the following:

@example
usage:  xset [-display host:dpy] option ...
  To turn bell off:
      -b                b off               b 0
  To set bell volume, pitch and duration:
       b [vol [pitch [dur]]]          b on
@end example

@node Automatic indentation
@section How do I tell Emacs to automatically indent a new line to the indentation of the previous line?
@cindex Indenting new lines
@cindex New lines, indenting of
@cindex Previous line, indenting according to
@cindex Text indentation

Such behavior is automatic (in Text mode) in Emacs 20 and later.  From the
@file{etc/NEWS} file for Emacs 20.2:

@example
** In Text mode, now only blank lines separate paragraphs.  This makes
it possible to get the full benefit of Adaptive Fill mode in Text mode,
and other modes derived from it (such as Mail mode).  @key{TAB} in Text
mode now runs the command @code{indent-relative}; this makes a practical
difference only when you use indented paragraphs.

If you want spaces at the beginning of a line to start a paragraph, use
the new mode, Paragraph Indent Text mode.
@end example

@cindex Prefixing lines
@cindex Fill prefix
If you have @code{auto-fill-mode} turned on (@pxref{Turning on auto-fill
by default}), you can tell Emacs to prefix every line with a certain
character sequence, the @dfn{fill prefix}.  Type the prefix at the
beginning of a line, position point after it, and then type @kbd{C-x .}
(@code{set-fill-prefix}) to set the fill prefix.  Thereafter,
auto-filling will automatically put the fill prefix at the beginning of
new lines, and @kbd{M-q} (@code{fill-paragraph}) will maintain any fill
prefix when refilling the paragraph.

If you have paragraphs with different levels of indentation, you will
have to set the fill prefix to the correct value each time you move to a
new paragraph.  There are many packages available to deal with this
(@pxref{Packages that do not come with Emacs}).  Look for ``fill'' and
``indent'' keywords for guidance.

@node Matching parentheses
@section How do I show which parenthesis matches the one I'm looking at?
@cindex Parentheses, matching
@cindex @file{paren.el}
@cindex Highlighting matching parentheses
@cindex Pairs of parentheses, highlighting
@cindex Matching parentheses

Call @code{show-paren-mode} in your @file{.emacs} file:

@lisp
(show-paren-mode 1)
@end lisp

You can also enable this mode by selecting the @samp{Paren Match
Highlighting} option from the @samp{Options} menu of the Emacs menu bar
at the top of any Emacs frame.

Alternatives to this mode include:

@itemize @bullet

@item
If you're looking at a right parenthesis (or brace or bracket) you can
delete it and reinsert it.  Emacs will momentarily move the cursor to
the matching parenthesis.

@item
@kbd{C-M-f} (@code{forward-sexp}) and @kbd{C-M-b} (@code{backward-sexp})
will skip over one set of balanced parentheses, so you can see which
parentheses match.  (You can train it to skip over balanced brackets
and braces at the same time by modifying the syntax table.)

@cindex Show matching paren as in @code{vi}
@item
Here is some Emacs Lisp that will make the @key{%} key show the matching
parenthesis, like in @code{vi}.  In addition, if the cursor isn't over a
parenthesis, it simply inserts a % like normal.

@lisp
;; By an unknown contributor

(global-set-key "%" 'match-paren)

(defun match-paren (arg)
  "Go to the matching paren if on a paren; otherwise insert %."
  (interactive "p")
  (cond ((looking-at "\\s\(") (forward-list 1) (backward-char 1))
        ((looking-at "\\s\)") (forward-char 1) (backward-list 1))
        (t (self-insert-command (or arg 1)))))
@end lisp

@end itemize

@node Hiding #ifdef lines
@section In C mode, can I show just the lines that will be left after @code{#ifdef} commands are handled by the compiler?
@cindex @code{#ifdef}, selective display of
@cindex @code{hide-ifdef-mode}
@cindex Hiding @code{#ifdef} text
@cindex Selectively displaying @code{#ifdef} code

@kbd{M-x hide-ifdef-mode}.  (This is a minor mode.)  You might also want
to investigate @file{cpp.el}, which is distributed with Emacs.

@node Repeating commands
@section How do I repeat a command as many times as possible?
@cindex Repeating commands many times
@cindex Commands, repeating many times
@cindex @code{.}, equivalent to @code{vi} command

As of Emacs 20.3, there is indeed a @code{repeat} command (@kbd{C-x z})
that repeats the last command.  If you preface it with a prefix
argument, the prefix arg is applied to the command.

You can also type @kbd{C-x @key{ESC} @key{ESC}}
(@code{repeat-complex-command}) to reinvoke commands that used the
minibuffer to get arguments.  In @code{repeat-complex-command} you can
type @kbd{M-p} and @kbd{M-n} (and also up-arrow and down-arrow, if your
keyboard has these keys) to scan through all the different complex
commands you've typed.

To repeat a set of commands, use keyboard macros.  Use @kbd{C-x (} and
@kbd{C-x )} to make a keyboard macro that invokes the command and then
type @kbd{C-x e}.  (@inforef{Keyboard Macros, Keyboard Macros, emacs}.)

If you're really desperate for the @code{.} command in @code{vi} that
redoes the last insertion/deletion, use VIPER, a @code{vi} emulation
mode which comes with Emacs, and which appears to support it.

@node Valid X resources
@section What are the valid X resource settings (i.e., stuff in .Xdefaults)?
@cindex Resources, X
@cindex X resources
@cindex Setting X resources

@inforef{X Resources, X Resources, emacs}.

You can also use a resource editor, such as editres (for X11R5 and
onwards), to look at the resource names for the menu bar, assuming Emacs
was compiled with the X toolkit.

@node Evaluating Emacs Lisp code
@section How do I execute (``evaluate'') a piece of Emacs Lisp code?
@cindex Evaluating Lisp code
@cindex Lisp forms, evaluating

There are a number of ways to execute (@dfn{evaluate}, in Lisp lingo) an
Emacs Lisp @dfn{form}:

@itemize @bullet

@item
If you want it evaluated every time you run Emacs, put it in a file
named @file{.emacs} in your home directory.  This is known as ``your
@file{.emacs} file,'' and contains all of your personal customizations.

@item
You can type the form in the @file{*scratch*} buffer, and then type
@key{LFD} (or @kbd{C-j}) after it.  The result of evaluating the form
will be inserted in the buffer.

@item
In @code{emacs-lisp-mode}, typing @kbd{C-M-x} evaluates a top-level form
before or around point.

@item
Typing @kbd{C-x C-e} in any buffer evaluates the Lisp form immediately
before point and prints its value in the echo area.

@item
Typing @kbd{M-:} or @kbd{M-x eval-expression} allows you to type a Lisp
form in the minibuffer which will be evaluated once you press @key{RET}.

@item
You can use @kbd{M-x load-file} to have Emacs evaluate all the Lisp
forms in a file.  (To do this from Lisp use the function @code{load}
instead.)

The functions @code{load-library}, @code{eval-region},
@code{eval-buffer}, @code{require}, and @code{autoload} are also
useful; see @ref{Emacs Lisp documentation}, if you want to learn more
about them.

@end itemize

@node Changing the length of a Tab
@section How do I change Emacs's idea of the @key{TAB} character's length?
@cindex Tab length
@cindex Length of tab character

Set the default value of the variable @code{tab-width}.  For example, to set
@key{TAB} stops every 10 characters, insert the following in your
@file{.emacs} file:

@lisp
(setq-default tab-width 10)
@end lisp

Do not confuse variable @code{tab-width} with variable
@code{tab-stop-list}.  The former is used for the display of literal
@key{TAB} characters.  The latter controls what characters are inserted
when you press the @key{TAB} character in certain modes.

@node Inserting text at the beginning of each line
@section How do I insert <some text> at the beginning of every line?
@cindex Prefixing a region with some text
@cindex Prefix character, inserting in mail/news replies
@cindex Replies to mail/news, inserting a prefix character
@cindex @code{mail-yank-prefix}
@cindex Mail replies, inserting a prefix character
@cindex News replies, inserting a prefix character

To do this to an entire buffer, type @kbd{M-< M-x replace-regexp
@key{RET} ^ @key{RET} your text @key{RET}}.

To do this to a region, use @code{string-insert-rectangle}.
Set the mark (@kbd{C-@key{SPC}}) at the beginning of the first line you
want to prefix, move the cursor to last line to be prefixed, and type
@kbd{M-x string-insert-rectangle @key{RET}}.  To do this for the whole
buffer, type @kbd{C-x h M-x string-insert-rectangle @key{RET}}.

If you are trying to prefix a yanked mail message with @samp{>}, you
might want to set the variable @code{mail-yank-prefix}.  In Message
buffers, you can even use @kbd{M-;} to cite yanked messages (@kbd{M-;}
runs the function @code{comment-region}, it is a general-purpose
mechanism to comment regions) (@pxref{Changing the included text prefix}).

@node Forcing the cursor to remain in the same column
@section How do I make Emacs behave like this: when I go up or down, the cursor should stay in the same column even if the line is too short?
@cindex @code{picture-mode}
@cindex Remaining in the same column, regardless of contents
@cindex Vertical movement in empty documents

Use @kbd{M-x picture-mode}.

See also the variable @code{track-eol} and the command
@code{set-goal-column} bound to @kbd{C-x C-n}
(@pxref{Moving Point, , , emacs, The GNU Emacs Manual}).

@node Forcing Emacs to iconify itself
@section How do I tell Emacs to iconify itself?
@cindex Iconification under the X Window System
@cindex X Window System and iconification
@cindex Suspending Emacs

@kbd{C-z} iconifies Emacs when running under X and suspends Emacs
otherwise.  @inforef{Frame Commands, Frame Commands, emacs}.

@node Using regular expressions
@section How do I use regexps (regular expressions) in Emacs?
@cindex Regexps
@cindex Regular expressions
@cindex Differences between Unix and Emacs regexps
@cindex Unix regexps, differences from Emacs
@cindex Text strings, putting regexps in

@inforef{Regexp Backslash, Regexp Backslash, emacs}.

The @code{or} operator is @samp{\|}, not @samp{|}, and the grouping operators
are @samp{\(} and @samp{\)}.  Also, the string syntax for a backslash is
@samp{\\}.  To specify a regular expression like @samp{xxx\(foo\|bar\)}
in a Lisp string, use @samp{xxx\\(foo\\|bar\\)}.

Note the doubled backslashes!

@itemize @bullet

@item
Unlike in Unix @file{grep}, @file{sed}, etc., a complement character set
(@samp{[^...]})  can match a newline character (@key{LFD} a.k.a.@:
@kbd{C-j} a.k.a.@: @samp{\n}), unless newline is mentioned as one of the
characters not to match.

@item
The character syntax regexps (e.g., @samp{\sw}) are not
meaningful inside character set regexps (e.g., @samp{[aeiou]}).  (This
is actually typical for regexp syntax.)

@end itemize

@node Replacing text across multiple files
@section How do I perform a replace operation across more than one file?
@cindex Replacing strings across files
@cindex Multiple files, replacing across
@cindex Files, replacing strings across multiple
@cindex Recursive search/replace operations

Dired mode (@kbd{M-x dired @key{RET}}, or @kbd{C-x d}) supports the
command @code{dired-do-query-replace-regexp} (@kbd{Q}), which allows
users to replace regular expressions in multiple files.

You can use this command to perform search/replace operations on
multiple files by following the following steps:

@itemize @bullet
@item
Assemble a list of files you want to operate on with either
@code{find-dired}, @code{find-name-dired} or @code{find-grep-dired}.

@item
Mark all files in the resulting Dired buffer using @kbd{t}.

@item
Use @kbd{Q} to start a @code{query-replace-regexp} session on the marked
files.

@item
To accept all replacements in each file, hit @kbd{!}.
@end itemize

Another way to do the same thing is to use the ``tags'' feature of
Emacs: it includes the command @code{tags-query-replace} which performs
a query-replace across all the files mentioned in the @file{TAGS} file.
@inforef{Tags Search, Tags Search, emacs}.

@node Documentation for etags
@section Where is the documentation for @code{etags}?
@cindex Documentation for @code{etags}
@cindex @code{etags}, documentation for

The @code{etags} man page should be in the same place as the
@code{emacs} man page.

Quick command-line switch descriptions are also available.  For example,
@samp{etags -H}.

@node Disabling backups
@section How do I disable backup files?
@cindex Backups, disabling
@cindex Disabling backups

You probably don't want to do this, since backups are useful, especially
when something goes wrong.

To avoid seeing backup files (and other ``uninteresting'' files) in Dired,
load @code{dired-x} by adding the following to your @file{.emacs} file:

@lisp
(add-hook 'dired-load-hook
          (lambda ()
           (require 'dired-x)))
@end lisp

With @code{dired-x} loaded, @kbd{M-o} toggles omitting in each dired buffer.
You can make omitting the default for new dired buffers by putting the
following in your @file{.emacs}:

@lisp
(add-hook 'dired-mode-hook 'dired-omit-toggle)
@end lisp

If you're tired of seeing backup files whenever you do an @samp{ls} at
the Unix shell, try GNU @code{ls} with the @samp{-B} option.  GNU
@code{ls} is part of the GNU Fileutils package, available from
@samp{ftp.gnu.org} and its mirrors (@pxref{Current GNU distributions}).

To disable or change the way backups are made, @inforef{Backup Names, ,
emacs}.

@cindex Backup files in a single directory
Beginning with Emacs 21.1, you can control where Emacs puts backup files
by customizing the variable @code{backup-directory-alist}.  This
variable's value specifies that files whose names match specific patters
should have their backups put in certain directories.  A typical use is
to add the element @code{("." . @var{dir})} to force Emacs to put
@strong{all} backup files in the directory @file{dir}.

@node Disabling auto-save-mode
@section How do I disable @code{auto-save-mode}?
@cindex Disabling @code{auto-save-mode}
@cindex Auto-saving
@cindex Saving at frequent intervals

You probably don't want to do this, since auto-saving is useful,
especially when Emacs or your computer crashes while you are editing a
document.

Instead, you might want to change the variable
@code{auto-save-interval}, which specifies how many keystrokes Emacs
waits before auto-saving.  Increasing this value forces Emacs to wait
longer between auto-saves, which might annoy you less.

You might also want to look into Sebastian Kremer's @code{auto-save}
package (@pxref{Packages that do not come with Emacs}).  This
package also allows you to place all auto-save files in one directory,
such as @file{/tmp}.

To disable or change how @code{auto-save-mode} works, @inforef{Auto
Save, , emacs}.

@node Going to a line by number
@section How can I go to a certain line given its number?
@cindex Going to a line by number
@cindex Compilation error messages
@cindex Recompilation

Are you sure you indeed need to go to a line by its number?  Perhaps all
you want is to display a line in your source file for which a compiler
printed an error message?  If so, compiling from within Emacs using the
@kbd{M-x compile} and @kbd{M-x recompile} commands is a much more
effective way of doing that.  Emacs automatically intercepts the compile
error messages, inserts them into a special buffer called
@code{*compilation*}, and lets you visit the locus of each message in
the source.  Type @kbd{C-x `} to step through the offending lines one by
one (starting with Emacs 22, you can also use @kbd{M-g M-p} and
@kbd{M-g M-n} to go to the previous and next matches directly).  Click
@kbd{Mouse-2} or press @key{RET} on a message text in the
@code{*compilation*} buffer to go to the line whose number is mentioned
in that message.

But if you indeed need to go to a certain text line, type @kbd{M-g M-g}
(which is the default binding of the @code{goto-line} function starting
with Emacs 22).  Emacs will prompt you for the number of the line and go
to that line.

You can do this faster by invoking @code{goto-line} with a numeric
argument that is the line's number.  For example, @kbd{C-u 286 M-g M-g}
will jump to line number 286 in the current buffer.

@node Modifying pull-down menus
@section How can I create or modify new pull-down menu options?
@cindex Pull-down menus, creating or modifying
@cindex Menus, creating or modifying
@cindex Creating new menu options
@cindex Modifying pull-down menus
@cindex Menus and keymaps
@cindex Keymaps and menus

Each menu title (e.g., @samp{File}, @samp{Edit}, @samp{Buffers})
represents a local or global keymap.  Selecting a menu title with the
mouse displays that keymap's non-@code{nil} contents in the form of a menu.

So to add a menu option to an existing menu, all you have to do is add a
new definition to the appropriate keymap.  Adding a @samp{Forward Word}
item to the @samp{Edit} menu thus requires the following Lisp code:

@lisp
(define-key global-map
  [menu-bar edit forward]
  '("Forward word" . forward-word))
@end lisp

@noindent
The first line adds the entry to the global keymap, which includes
global menu bar entries.  Replacing the reference to @code{global-map}
with a local keymap would add this menu option only within a particular
mode.

The second line describes the path from the menu-bar to the new entry.
Placing this menu entry underneath the @samp{File} menu would mean
changing the word @code{edit} in the second line to @code{file}.

The third line is a cons cell whose first element is the title that will
be displayed, and whose second element is the function that will be
called when that menu option is invoked.

To add a new menu, rather than a new option to an existing menu, we must
define an entirely new keymap:

@lisp
(define-key global-map [menu-bar words]
  (cons "Words" (make-sparse-keymap "Words")))
@end lisp

The above code creates a new sparse keymap, gives it the name
@samp{Words}, and attaches it to the global menu bar.  Adding the
@samp{Forward Word} item to this new menu would thus require the
following code:

@lisp
(define-key global-map
  [menu-bar words forward]
  '("Forward word" . forward-word))
@end lisp

@noindent
Note that because of the way keymaps work, menu options are displayed
with the more recently defined items at the top.  Thus if you were to
define menu options @samp{foo}, @samp{bar}, and @samp{baz} (in that
order), the menu option @samp{baz} would appear at the top, and
@samp{foo} would be at the bottom.

One way to avoid this problem is to use the function @code{define-key-after},
which works the same as @code{define-key}, but lets you modify where items
appear.  The following Lisp code would insert the @samp{Forward Word}
item in the @samp{Edit} menu immediately following the @samp{Undo} item:

@lisp
(define-key-after
  (lookup-key global-map [menu-bar edit])
  [forward]
  '("Forward word" . forward-word)
  'undo)
@end lisp

Note how the second and third arguments to @code{define-key-after} are
different from those of @code{define-key}, and that we have added a new
(final) argument, the function after which our new key should be
defined.

To move a menu option from one position to another, simply evaluate
@code{define-key-after} with the appropriate final argument.

More detailed information---and more examples of how to create and
modify menu options---are in the @cite{Emacs Lisp Reference Manual}, under
``Menu Keymaps.''  (@xref{Emacs Lisp documentation}, for information on
this manual.)

@node Deleting menus and menu options
@section How do I delete menus and menu options?
@cindex Deleting menus and menu options
@cindex Menus, deleting

The simplest way to remove a menu is to set its keymap to @samp{nil}.
For example, to delete the @samp{Words} menu (@pxref{Modifying pull-down
menus}), use:

@lisp
(define-key global-map [menu-bar words] nil)
@end lisp

Similarly, removing a menu option requires redefining a keymap entry to
@code{nil}.  For example, to delete the @samp{Forward word} menu option
from the @samp{Edit} menu (we added it in @ref{Modifying pull-down
menus}), use:

@lisp
(define-key global-map [menu-bar edit forward] nil)
@end lisp

@node Turning on syntax highlighting
@section How do I turn on syntax highlighting?
@cindex Syntax highlighting
@cindex @code{font-lock-mode}
@cindex Highlighting based on syntax
@cindex Colorizing text
@cindex FAQ, @code{font-lock-mode}

@code{font-lock-mode} is the standard way to have Emacs perform syntax
highlighting in the current buffer.  It is enabled by default in Emacs
22.1 and later.

With @code{font-lock-mode} turned on, different types of text will
appear in different colors.  For instance, in a programming mode,
variables will appear in one face, keywords in a second, and comments in
a third.

To turn @code{font-lock-mode} off within an existing buffer, use
@kbd{M-x font-lock-mode @key{RET}}.

In Emacs 21 and earlier versions, you could use the following code in
your @file{.emacs} file to turn on @code{font-lock-mode} globally:

@lisp
(global-font-lock-mode 1)
@end lisp

Highlighting a buffer with @code{font-lock-mode} can take quite a while,
and cause an annoying delay in display, so several features exist to
work around this.

@cindex Just-In-Time syntax highlighting
In Emacs 21 and later, turning on @code{font-lock-mode} automatically
activates the new @dfn{Just-In-Time fontification} provided by
@code{jit-lock-mode}.  @code{jit-lock-mode} defers the fontification of
portions of buffer until you actually need to see them, and can also
fontify while Emacs is idle.  This makes display of the visible portion
of a buffer almost instantaneous.  For details about customizing
@code{jit-lock-mode}, type @kbd{C-h f jit-lock-mode @key{RET}}.

@cindex Levels of syntax highlighting
@cindex Decoration level, in @code{font-lock-mode}
In versions of Emacs before 21, different levels of decoration are
available, from slight to gaudy.  More decoration means you need to wait
more time for a buffer to be fontified (or a faster machine).  To
control how decorated your buffers should become, set the value of
@code{font-lock-maximum-decoration} in your @file{.emacs} file, with a
@code{nil} value indicating default (usually minimum) decoration, and a
@code{t} value indicating the maximum decoration.  For the gaudiest
possible look, then, include the line

@lisp
(setq font-lock-maximum-decoration t)
@end lisp

@noindent
in your @file{.emacs} file.  You can also set this variable such that
different modes are highlighted in a different ways; for more
information, see the documentation for
@code{font-lock-maximum-decoration} with @kbd{C-h v} (or @kbd{M-x
describe-variable @key{RET}}).

Also see the documentation for the function @code{font-lock-mode},
available by typing @kbd{C-h f font-lock-mode} (@kbd{M-x
describe-function @key{RET} font-lock-mode @key{RET}}).

To print buffers with the faces (i.e., colors and fonts) intact, use
@kbd{M-x ps-print-buffer-with-faces} or @kbd{M-x
ps-print-region-with-faces}.  You will need a way to send text to a
PostScript printer, or a PostScript interpreter such as Ghostscript;
consult the documentation of the variables @code{ps-printer-name},
@code{ps-lpr-command}, and @code{ps-lpr-switches} for more details.

@node Scrolling only one line
@section How can I force Emacs to scroll only one line when I move past the bottom of the screen?
@cindex Scrolling only one line
@cindex Reducing the increment when scrolling

Customize the @code{scroll-conservatively} variable with @kbd{M-x
customize-variable @key{RET} scroll-conservatively @key{RET}} and set it
to a large value like, say, 10000.  For an explanation of what this
means, @inforef{Auto Scrolling, Auto Scrolling, emacs}.

Alternatively, use the following Lisp form in your @file{.emacs}:

@lisp
(setq scroll-conservatively most-positive-fixnum)
@end lisp

@node Editing MS-DOS files
@section How can I edit MS-DOS files using Emacs?
@cindex Editing MS-DOS files
@cindex MS-DOS files, editing
@cindex Microsoft files, editing
@cindex Windows files, editing

As of Emacs 20, detection and handling of MS-DOS (and Windows) files is
performed transparently.  You can open MS-DOS files on a Unix system,
edit it, and save it without having to worry about the file format.

When editing an MS-DOS style file, the mode line will indicate that it
is a DOS file.  On Unix and GNU/Linux systems, and also on a Macintosh,
the string @samp{(DOS)} will appear near the left edge of the mode line;
on DOS and Windows, where the DOS end-of-line (EOL) format is the
default, a backslash (@samp{\}) will appear in the mode line.

@node Filling paragraphs with a single space
@section How can I tell Emacs to fill paragraphs with a single space after each period?
@cindex One space following periods
@cindex Single space following periods
@cindex Periods, one space following

Add the following line to your @file{.emacs} file:

@lisp
(setq sentence-end-double-space nil)
@end lisp

@node Escape sequences in shell output
@section Why these strange escape sequences from @code{ls} from the Shell mode?
@cindex Escape sequences in @code{ls} output
@cindex @code{ls} in Shell mode

In many systems, @code{ls} is aliased to @samp{ls --color}, which
prints using ANSI color escape sequences.  Emacs version 21.1 and
later includes the @code{ansi-color} package, which lets Shell mode
recognize these escape sequences.  In Emacs 23.2 and later, the
package is enabled by default; in earlier versions you can enable it
by typing @kbd{M-x ansi-color-for-comint-mode} in the Shell buffer, or
by adding @code{(add-hook 'shell-mode-hook
'ansi-color-for-comint-mode-on)} to your init file.

In Emacs versions before 21.1, the @code{ansi-color} package is not
included.  In that case, you need to unalias @code{ls} for interactive
shells running in Emacs; this can be done by checking the @code{EMACS}
variable in the environment.

@node Fullscreen mode on MS-Windows
@section How can I start Emacs in fullscreen mode on MS-Windows?
@cindex Maximize frame
@cindex Fullscreen mode

Use the function @code{w32-send-sys-command}.  For example, you can
put the following in your @file{.emacs} file:

@lisp
(add-hook 'term-setup-hook
          #'(lambda () (w32-send-sys-command ?\xF030)))
@end lisp

To avoid the slightly distracting visual effect of Emacs starting with
its default frame size and then growing to fullscreen, you can add an
@samp{Emacs.Geometry} entry to the Windows registry settings (see
@pxref{(emacs)X Resources}).

To compute the correct values for width and height, first maximize the
Emacs frame and then evaluate @code{(frame-height)} and
@code{(frame-width)} with @kbd{M-:}.

@c ------------------------------------------------------------
@node Bugs and problems
@chapter Bugs and problems
@cindex Bugs and problems

The Emacs manual lists some common kinds of trouble users could get
into, see @ref{Lossage, , Dealing with Emacs Trouble, emacs, The GNU
Emacs Manual}, so you might look there if the problem you encounter
isn't described in this chapter.  If you decide you've discovered a bug,
see @ref{Bugs, , Reporting Bugs, emacs, The GNU Emacs Manual}, for
instructions how to do that.

The file @file{etc/PROBLEMS} in the Emacs distribution lists various
known problems with building and using Emacs on specific platforms;
type @kbd{C-h C-p} to read it.

@menu
* Problems with very large files::
* ^M in the shell buffer::
* Problems with Shell Mode::
* Termcap/Terminfo entries for Emacs::
* Errors with init files::
* Emacs ignores X resources::
* Emacs ignores frame parameters::
* Editing files with $ in the name::
* Shell mode loses the current directory::
* Security risks with Emacs::
* Dired claims that no file is on this line::
@end menu

@node Problems with very large files
@section Does Emacs have problems with files larger than 8 megabytes?
@cindex Very large files, opening
@cindex Large files, opening
@cindex Opening very large files
@cindex Maximum file size
@cindex Files, maximum size

Old versions (i.e., anything before 19.29) of Emacs had problems editing
files larger than 8 megabytes.  In versions 19.29 and later, the maximum
buffer size is at least 2^27-1, or 134,217,727 bytes, or 132 MBytes.
The maximum buffer size on 32-bit machines increased to 256 MBytes in
Emacs 22, and again to 512 MBytes in Emacs 23.2.

Emacs compiled on a 64-bit machine can handle much larger buffers.

@node ^M in the shell buffer
@section How do I get rid of @samp{^M} or echoed commands in my shell buffer?
@cindex Shell buffer, echoed commands and @samp{^M} in
@cindex Echoed commands in @code{shell-mode}

Try typing @kbd{M-x shell-strip-ctrl-m @key{RET}} while in @code{shell-mode} to
make them go away.  If that doesn't work, you have several options:

For @code{tcsh}, put this in your @file{.cshrc} (or @file{.tcshrc})
file:

@example
if ($?EMACS) then
    if ("$EMACS" =~ /*) then
        if ($?tcsh) unset edit
        stty nl
    endif
endif
@end example

Or put this in your @file{.emacs_tcsh} or @file{~/.emacs.d/init_tcsh.sh} file:

@example
unset edit
stty nl
@end example

Alternatively, use @code{csh} in your shell buffers instead of
@code{tcsh}.  One way is:

@lisp
(setq explicit-shell-file-name "/bin/csh")
@end lisp

@noindent
and another is to do this in your @file{.cshrc} (or @file{.tcshrc})
file:

@example
setenv ESHELL /bin/csh
@end example

@noindent
(You must start Emacs over again with the environment variable properly
set for this to take effect.)

You can also set the @code{ESHELL} environment variable in Emacs Lisp
with the following Lisp form,

@lisp
(setenv "ESHELL" "/bin/csh")
@end lisp

The above solutions try to prevent the shell from producing the
@samp{^M} characters in the first place.  If this is not possible
(e.g., if you use a Windows shell), you can get Emacs to remove these
characters from the buffer by adding this to your @file{.emacs} init
file:

@smalllisp
(add-hook 'comint-output-filter-functions 'shell-strip-ctrl-m)
@end smalllisp

On a related note: if your shell is echoing your input line in the shell
buffer, you might want to customize the @code{comint-process-echoes}
variable in your shell buffers, or try the following command in your
shell start-up file:

@example
stty -icrnl -onlcr -echo susp ^Z
@end example

@node Problems with Shell Mode
@section Why do I get an error message when I try to run @kbd{M-x shell}?

@cindex Shell Mode, problems
@cindex @code{explicit-shell-file-name}
This might happen because Emacs tries to look for the shell in a wrong
place.  If you know where your shell executable is, set the variable
@code{explicit-shell-file-name} in your @file{.emacs} file to point to
its full file name.

@cindex Antivirus programs, and Shell Mode
Some people have trouble with Shell Mode on MS-Windows because of
intrusive antivirus software; disabling the resident antivirus program
solves the problems in those cases.

@node Termcap/Terminfo entries for Emacs
@section Where is the termcap/terminfo entry for terminal type @samp{emacs}?
@cindex Termcap
@cindex Terminfo
@cindex Emacs entries for termcap/terminfo

The termcap entry for terminal type @samp{emacs} is ordinarily put in
the @samp{TERMCAP} environment variable of subshells.  It may help in
certain situations (e.g., using rlogin from shell buffer) to add an
entry for @samp{emacs} to the system-wide termcap file.  Here is a
correct termcap entry for @samp{emacs}:

@example
emacs:tc=unknown:
@end example

To make a terminfo entry for @samp{emacs}, use @code{tic} or
@code{captoinfo}.  You need to generate
@file{/usr/lib/terminfo/e/emacs}.  It may work to simply copy
@file{/usr/lib/terminfo/d/dumb} to @file{/usr/lib/terminfo/e/emacs}.

Having a termcap/terminfo entry will not enable the use of full screen
programs in shell buffers.  Use @kbd{M-x terminal-emulator} for that
instead.

A workaround to the problem of missing termcap/terminfo entries is to
change terminal type @samp{emacs} to type @samp{dumb} or @samp{unknown}
in your shell start up file.  @code{csh} users could put this in their
@file{.cshrc} files:

@example
if ("$term" == emacs) set term=dumb
@end example

@node Errors with init files
@section Why does Emacs say @samp{Error in init file}?
@cindex Error in @file{.emacs}
@cindex Error in init file
@cindex Init file, errors in
@cindex @file{.emacs} file, errors in
@cindex Debugging @file{.emacs} file

An error occurred while loading either your @file{.emacs} file or the
system-wide file @file{site-lisp/default.el}.  Emacs 21.1 and later pops the
@file{*Messages*} buffer, and puts there some additional information
about the error, to provide some hints for debugging.

For information on how to debug your @file{.emacs} file, see
@ref{Debugging a customization file}.

It may be the case that you need to load some package first, or use a
hook that will be evaluated after the package is loaded.  A common case
of this is explained in @ref{Terminal setup code works after Emacs has
begun}.

@node Emacs ignores X resources
@section Why does Emacs ignore my X resources (my .Xdefaults file)?
@cindex X resources being ignored
@cindex Ignored X resources
@cindex @file{.Xdefaults}

As of version 19, Emacs searches for X resources in the files specified
by the following environment variables:

@itemize @bullet

@item @code{XFILESEARCHPATH}
@item @code{XUSERFILESEARCHPATH}
@item @code{XAPPLRESDIR}

@end itemize

This emulates the functionality provided by programs written using the
Xt toolkit.

@code{XFILESEARCHPATH} and @code{XUSERFILESEARCHPATH} should be a list
of file names separated by colons.  @code{XAPPLRESDIR} should be a list
of directory names separated by colons.

Emacs searches for X resources:

@enumerate

@item
specified on the command line, with the @samp{-xrm RESOURCESTRING} option,

@item
then in the value of the @samp{XENVIRONMENT} environment variable,

@itemize @minus

@item
or if that is unset, in the file named
@file{~/.Xdefaults-@var{hostname}} if it exists (where @var{hostname} is
the name of the machine Emacs is running on),

@end itemize

@item
then in the screen-specific and server-wide resource properties provided
by the server,

@itemize @minus

@item
or if those properties are unset, in the file named @file{~/.Xdefaults}
if it exists,

@end itemize

@item
then in the files listed in @samp{XUSERFILESEARCHPATH},

@itemize @minus

@item
or in files named @file{@var{lang}/Emacs} in directories listed in
@samp{XAPPLRESDIR} (where @var{lang} is the value of the @code{LANG}
environment variable), if the @samp{LANG} environment variable is set,
@item
or in files named Emacs in the directories listed in @samp{XAPPLRESDIR}
@item
or in @file{~/@var{lang}/Emacs} (if the @code{LANG} environment variable
is set),
@item
or in @file{~/Emacs},

@end itemize

@item
then in the files listed in  @code{XFILESEARCHPATH}.

@end enumerate

@node Emacs ignores frame parameters
@section Why don't my customizations of the frame parameters work?
@cindex Frame parameters

This probably happens because you have set the frame parameters in the
variable @code{initial-frame-alist}.  That variable holds parameters
used only for the first frame created when Emacs starts.  To customize
the parameters of all frames, change the variable
@code{default-frame-alist} instead.

These two variables exist because many users customize the initial frame
in a special way.  For example, you could determine the position and
size of the initial frame, but would like to control the geometry of the
other frames by individually positioning each one of them.


@node Editing files with $ in the name
@section How do I edit a file with a @samp{$} in its name?
@cindex Editing files with @samp{$} in the name
@cindex @samp{$} in file names
@cindex File names containing @samp{$}, editing

When entering a file name in the minibuffer, Emacs will attempt to expand
a @samp{$} followed by a word as an environment variable.  To suppress
this behavior, type @kbd{$$} instead.

@node Shell mode loses the current directory
@section Why does shell mode lose track of the shell's current directory?
@cindex Current directory and @code{shell-mode}
@cindex @code{shell-mode} and current directory
@cindex Directory, current in @code{shell-mode}

Emacs has no way of knowing when the shell actually changes its
directory.  This is an intrinsic limitation of Unix.  So it tries to
guess by recognizing @samp{cd} commands.  If you type @kbd{cd} followed
by a directory name with a variable reference (@kbd{cd $HOME/bin}) or
with a shell metacharacter (@kbd{cd ../lib*}), Emacs will fail to
correctly guess the shell's new current directory.  A huge variety of
fixes and enhancements to shell mode for this problem have been written
to handle this problem (@pxref{Finding a package with particular
functionality}).

You can tell Emacs the shell's current directory with the command
@kbd{M-x dirs}.

@node Security risks with Emacs
@section Are there any security risks in Emacs?
@cindex Security with Emacs
@cindex @samp{movemail} and security
@cindex @code{file-local-variable} and security
@cindex Synthetic X events and security
@cindex X events and security

@itemize @bullet

@item
The @file{movemail} incident.  (No, this is not a risk.)

In his book @cite{The Cuckoo's Egg}, Cliff Stoll describes this in
chapter 4.  The site at LBL had installed the @file{/etc/movemail}
program setuid root.  (As of version 19, @file{movemail} is in your
architecture-specific directory; type @kbd{C-h v exec-directory
@key{RET}} to see what it is.)  Since @code{movemail} had not been
designed for this situation, a security hole was created and users could
get root privileges.

@code{movemail} has since been changed so that this security hole will
not exist, even if it is installed setuid root.  However,
@code{movemail} no longer needs to be installed setuid root, which
should eliminate this particular risk.

We have heard unverified reports that the 1988 Internet worm took
advantage of this configuration problem.

@item
The @code{file-local-variable} feature.  (Yes, a risk, but easy to
change.)

There is an Emacs feature that allows the setting of local values for
variables when editing a file by including specially formatted text near
the end of the file.  This feature also includes the ability to have
arbitrary Emacs Lisp code evaluated when the file is visited.
Obviously, there is a potential for Trojan horses to exploit this
feature.

As of Emacs 22, Emacs has a list of local variables that are known to
be safe to set.  If a file tries to set any variable outside this
list, it asks the user to confirm whether the variables should be set.
You can also tell Emacs whether to allow the evaluation of Emacs Lisp
code found at the bottom of files by setting the variable
@code{enable-local-eval}.

For more information, @inforef{File Variables, File Variables, emacs}.

@item
Synthetic X events.  (Yes, a risk; use @samp{MIT-MAGIC-COOKIE-1} or
better.)

Emacs accepts synthetic X events generated by the @code{SendEvent}
request as though they were regular events.  As a result, if you are
using the trivial host-based authentication, other users who can open X
connections to your X workstation can make your Emacs process do
anything, including run other processes with your privileges.

The only fix for this is to prevent other users from being able to open
X connections.  The standard way to prevent this is to use a real
authentication mechanism, such as @samp{MIT-MAGIC-COOKIE-1}.  If using
the @code{xauth} program has any effect, then you are probably using
@samp{MIT-MAGIC-COOKIE-1}.  Your site may be using a superior
authentication method; ask your system administrator.

If real authentication is not a possibility, you may be satisfied by
just allowing hosts access for brief intervals while you start your X
programs, then removing the access.  This reduces the risk somewhat by
narrowing the time window when hostile users would have access, but
@emph{does not eliminate the risk}.

On most computers running Unix and X, you enable and disable
access using the @code{xhost} command.  To allow all hosts access to
your X server, use

@example
xhost +
@end example

@noindent
at the shell prompt, which (on an HP machine, at least) produces the
following message:

@example
access control disabled, clients can connect from any host
@end example

To deny all hosts access to your X server (except those explicitly
allowed by name), use

@example
xhost -
@end example

On the test HP computer, this command generated the following message:

@example
access control enabled, only authorized clients can connect
@end example

@end itemize

@node Dired claims that no file is on this line
@section Dired says, @samp{no file on this line} when I try to do something.
@cindex Dired does not see a file

Dired uses a regular expression to find the beginning of a file name.
In a long Unix-style directory listing (@samp{ls -l}), the file name
starts after the date.  The regexp has thus been written to look for the
date.  By default, it should understand dates and times regardless of
the language, but if your directory listing has an unusual format, Dired
may get confused.

There are two approaches to solving this.  The first one involves
setting things up so that @samp{ls -l} outputs a more standard format.
See your OS manual for more information.

The second approach involves changing the regular expression used by
dired, @code{directory-listing-before-filename-regexp}.

@c ------------------------------------------------------------
@node Compiling and installing Emacs
@chapter    Compiling and installing Emacs
@cindex    Compiling and installing Emacs

@menu
* Installing Emacs::
* Problems building Emacs::
@end menu

@node Installing Emacs
@section How do I install Emacs?
@cindex Installing Emacs
@cindex Unix systems, installing Emacs on
@cindex Downloading and installing Emacs
@cindex Building Emacs from source
@cindex Source code, building Emacs from

This answer is meant for users of Unix and Unix-like systems.  Users of
other operating systems should see the series of questions beginning
with @ref{Emacs for MS-DOS}, which describe where to get non-Unix source
and binaries, and how to install Emacs on those systems.

Most GNU/Linux distributions provide pre-built Emacs packages.
If Emacs is not installed already, you can install it by running (as
root) a command such as @samp{yum install emacs} (Red Hat and
derivatives) or @samp{apt-get install emacs} (Debian and derivatives).

If you want to compile Emacs yourself, read the file @file{INSTALL} in
the source distribution.  In brief:

@itemize @bullet

@item
First download the Emacs sources.  @xref{Current GNU distributions}, for
a list of ftp sites that make them available.  On @file{ftp.gnu.org},
the main GNU distribution site, sources are available as

@c Don't include VER in the file name, because pretests are not there.
@uref{ftp://ftp.gnu.org/pub/gnu/emacs/emacs-VERSION.tar.gz}

(Replace @samp{VERSION} with the relevant version number, e.g. @samp{23.1}.)

@item
Next uncompress and extract the source files.  This requires
the @code{gzip} and @code{tar} programs, which are standard utilities.
If your system does not have them, these can also be downloaded from
@file{ftp.gnu.org}.

GNU @code{tar} can uncompress and extract in a single-step:

@example
tar -zxvf emacs-VERSION.tar.gz
@end example

@item
At this point, the Emacs sources should be sitting in a directory called
@file{emacs-VERSION}.  On most common Unix and Unix-like systems,
you should be able to compile Emacs with the following commands:

@example
cd emacs-VERSION
./configure         # configure Emacs for your particular system
make                # use Makefile to build components, then Emacs
@end example

If the @code{make} completes successfully, the odds are fairly good that
the build has gone well.  (@xref{Problems building Emacs}, if you weren't
successful.)

@item
By default, Emacs is installed in @file{/usr/local}.  To actually
install files, become the superuser and type

@example
make install
@end example

Note that @samp{make install} will overwrite @file{/usr/local/bin/emacs}
and any Emacs Info files that might be in @file{/usr/local/share/info/}.

@end itemize

@node Problems building Emacs
@section What should I do if I have trouble building Emacs?
@cindex Problems building Emacs
@cindex Errors when building Emacs

First look in the file @file{etc/PROBLEMS} (where you unpack the Emacs
source) to see if there is already a solution for your problem.  Next,
look for other questions in this FAQ that have to do with Emacs
installation and compilation problems.

If you'd like to have someone look at your problem and help solve it,
see @ref{Help installing Emacs}.

If you cannot find a solution in the documentation, please report the
problem (@pxref{Reporting bugs}).


@c ------------------------------------------------------------
@node Finding Emacs and related packages
@chapter Finding Emacs and related packages
@cindex Finding Emacs and related packages

@menu
* Finding Emacs on the Internet::
* Finding a package with particular functionality::
* Packages that do not come with Emacs::
* Current GNU distributions::
* Difference between Emacs and XEmacs::
* Emacs for minimalists::
* Emacs for MS-DOS::
* Emacs for MS-Windows::
* Emacs for GNUstep::
* Emacs for Mac OS X::
@end menu

@node Finding Emacs on the Internet
@section Where can I get Emacs on the net?
@cindex Finding Emacs on the Internet
@cindex Downloading Emacs

Information on downloading Emacs is available at
@uref{http://www.gnu.org/software/emacs/, the Emacs home-page}.

@xref{Installing Emacs}, for information on how to obtain and build the latest
version of Emacs, and see @ref{Current GNU distributions}, for a list of
archive sites that make GNU software available.

@node Finding a package with particular functionality
@section How do I find a Emacs Lisp package that does XXX?
@cindex Package, finding
@cindex Finding an Emacs Lisp package
@cindex Functionality, finding a particular package

First of all, you should check to make sure that the package isn't
already available.  For example, typing @kbd{M-x apropos @key{RET}
wordstar @key{RET}} lists all functions and variables containing the
string @samp{wordstar}.

It is also possible that the package is on your system, but has not been
loaded.  To see which packages are available for loading, look through
your computer's lisp directory (@pxref{File-name conventions}).  The Lisp
source to most packages contains a short description of how they
should be loaded, invoked, and configured---so before you use or
modify a Lisp package, see if the author has provided any hints in the
source code.

The command @kbd{C-h p} (@code{finder-by-keyword}) allows you to browse
the constituent Emacs packages.

For advice on how to find extra packages that are not part of Emacs,
see @ref{Packages that do not come with Emacs}.

@node Packages that do not come with Emacs
@section Where can I get Emacs Lisp packages that don't come with Emacs?
@cindex Unbundled packages
@cindex Finding other packages
@cindex Lisp packages that do not come with Emacs
@cindex Packages, those that do not come with Emacs
@cindex Emacs Lisp List
@cindex Emacs Lisp Archive

@uref{http://www.damtp.cam.ac.uk/user/sje30/emacs/ell.html, The Emacs Lisp
List (ELL)}, maintained by @email{S.J.Eglen@@damtp.cam.ac.uk, Stephen Eglen},
aims to provide one compact list with links to all of the current Emacs
Lisp files on the Internet.  The ELL can be browsed over the web, or
from Emacs with @uref{http://www.damtp.cam.ac.uk/user/sje30/emacs/ell.el,
the @file{ell} package}.

Many authors post their packages to the @uref{news:gnu.emacs.sources,
Emacs sources newsgroup}.  You can search the archives of this
group with @uref{http://groups.google.com/group/gnu.emacs.sources, Google},
or @uref{http://dir.gmane.org/gmane.emacs.sources, Gmane}, for example.

Several packages are stored in
@uref{http://emacswiki.org/elisp/, the Lisp area of the Emacs Wiki}.

Read the file @file{etc/MORE.STUFF} for more information about
external packages.

@node Current GNU distributions
@section Where can I get other up-to-date GNU stuff?
@cindex Current GNU distributions
@cindex Sources for current GNU distributions
@cindex Stuff, current GNU
@cindex Up-to-date GNU stuff
@cindex Finding current GNU software
@cindex Official GNU software sites

The most up-to-date official GNU software is normally kept at

@uref{ftp://ftp.gnu.org/pub/gnu}

A list of sites mirroring @samp{ftp.gnu.org} can be found at

@uref{http://www.gnu.org/order/ftp.html}

@node Difference between Emacs and XEmacs
@section What is the difference between Emacs and XEmacs (formerly Lucid Emacs)?
@cindex XEmacs
@cindex Difference Emacs and XEmacs
@cindex Lucid Emacs
@cindex Epoch

XEmacs is a branch version of Emacs.  It was first called Lucid Emacs,
and was initially derived from a prerelease version of Emacs 19.  In
this FAQ, we use the name ``Emacs'' only for the official version.

Emacs and XEmacs each come with Lisp packages that are lacking in the
other.  The two versions have some significant differences at the Lisp
programming level.  Their current features are roughly comparable,
though the support for some operating systems, character sets and
specific packages might be quite different.

Some XEmacs code has been contributed to Emacs, and we would like to
use other parts, but the earlier XEmacs maintainers did not always
keep track of the authors of contributed code, which makes it
impossible for the FSF to get copyright papers signed for that code.
(The FSF requires these papers for all the code included in the Emacs
release, aside from generic C support packages that retain their
separate identity and are not integrated into the code of Emacs
proper.)

If you want to talk about these two versions and distinguish them,
please call them ``Emacs'' and ``XEmacs.''  To contrast ``XEmacs''
with ``GNU Emacs'' would be misleading, since XEmacs too has its
origin in the work of the GNU Project.  Terms such as ``Emacsen'' and
``(X)Emacs'' are not wrong, but they are not very clear, so it
is better to write ``Emacs and XEmacs.''

@node Emacs for minimalists
@section I don't have enough disk space to install Emacs
@cindex Zile
@cindex Not enough disk space to install Emacs

GNU Zile is a lightweight Emacs clone.  Zile is short for @samp{Zile Is
Lossy Emacs}.  It has all of Emacs's basic editing features.  The Zile
binary typically has a size of about 130 kbytes, so this can be useful
if you are in an extremely space-restricted environment.  More
information is available from

@uref{http://www.gnu.org/software/zile/}


@node Emacs for MS-DOS
@section Where can I get Emacs for MS-DOS?
@cindex MS-DOS, Emacs for
@cindex DOS, Emacs for
@cindex Compiling Emacs for DOS
@cindex Emacs for MS-DOS

To build Emacs from source for MS-DOS, see the instructions in the file
@file{msdos/INSTALL} in the distribution.  The DOS port builds and runs
on plain DOS, and also on all versions of MS-Windows from version 3.X
onwards, including Windows XP and Vista.

The file @file{etc/PROBLEMS} contains some additional information
regarding Emacs under MS-DOS.

A pre-built binary distribution of the old Emacs 20 is available, as
described at

@uref{ftp://ftp.delorie.com/pub/djgpp/current/v2gnu/emacs.README}

For a list of other MS-DOS implementations of Emacs (and Emacs
look-alikes), consult the list of ``Emacs implementations and literature,''
available at

@uref{http://www.finseth.com/emacs.html}

Note that while many of these programs look similar to Emacs, they often
lack certain features, such as the Emacs Lisp extension language.

@node Emacs for MS-Windows
@section Where can I get Emacs for Microsoft Windows?
@cindex FAQ for Emacs on MS-Windows
@cindex Emacs for MS-Windows
@cindex Microsoft Windows, Emacs for

There is a @uref{http://www.gnu.org/software/emacs/windows/ntemacs.html,
separate FAQ} for Emacs on MS-Windows.  For MS-DOS, @pxref{Emacs for MS-DOS}.


@node Emacs for GNUstep
@section Where can I get Emacs for GNUstep?
@cindex GNUstep, Emacs for

Beginning with version 23.1, Emacs supports GNUstep natively.
See the file @file{nextstep/INSTALL} in the distribution.

@node Emacs for Mac OS X
@section Where can I get Emacs for Mac OS X?
@cindex Apple computers, Emacs for
@cindex Macintosh, Emacs for
@cindex Mac OS X, Emacs for

Beginning with version 22.1, Emacs supports Mac OS X natively.
See the file @file{nextstep/INSTALL} in the distribution.

@c ------------------------------------------------------------
@node Major packages and programs
@chapter Major packages and programs
@cindex Major packages and programs

@menu
* VM::
* AUCTeX::
* BBDB::
* Spell-checkers::
* Emacs/W3::
* EDB::
* JDEE::
@end menu

@node VM
@section VM (View Mail) --- another mail reader within Emacs, with MIME support
@cindex VM
@cindex Alternative mail software
@cindex View Mail
@cindex E-mail reader, VM

@table @b

@item Web site
@uref{http://launchpad.net/vm}
(was @uref{http://www.nongnu.org/viewmail/})

@item Informational newsgroup
@uref{news:gnu.emacs.vm.info}@*

@item Bug reports newsgroup
@uref{news:gnu.emacs.vm.bug}@*
@end table

VM was originally written by @uref{http://www.wonderworks.com/vm/,Kyle Jones}.
@uref{ftp://ftp.wonderworks.com/pub/vm/,Older versions} of VM remain
available.


@node AUCTeX
@section AUC@TeX{} --- enhanced @TeX{} modes with debugging facilities
@cindex Mode for @TeX{}
@cindex @TeX{} mode
@cindex AUC@TeX{} mode for editing @TeX{}
@cindex Writing and debugging @TeX{}

AUC@TeX{} is a set of sophisticated major modes for @TeX{}, LaTeX,
ConTeXt, and Texinfo offering context-sensitive syntax highlighting,
indentation, formatting and folding, macro completion, @TeX{} shell
functionality, and debugging.  Be also sure to check out
@ref{Introduction, RefTeX, Introduction, reftex, Ref@TeX{} User Manual}.
Current versions of AUC@TeX{} include the
@uref{http://www.gnu.org/software/auctex/preview-latex.html,preview-latex}
package for WYSIWYG previews of various LaTeX constructs in the Emacs
source buffer.

@uref{http://www.gnu.org/software/auctex/, AUCTeX}

@node BBDB
@section BBDB --- personal Info Rolodex integrated with mail/news readers
@cindex BBDB
@cindex Rolodex-like functionality
@cindex Integrated contact database
@cindex Contact database
@cindex Big Brother Database
@cindex Address book

@uref{http://bbdb.sourceforge.net/, The Insidious Big Brother Database}

@node Spell-checkers
@section Spell-checkers
@cindex Spell-checker
@cindex Checking spelling
@cindex Ispell
@cindex Aspell
@cindex Hunspell

Various spell-checkers are compatible with Emacs, including:

@table @b

@item GNU Aspell
@uref{http://aspell.net/}

@item Ispell
@uref{http://fmg-www.cs.ucla.edu/geoff/ispell.html}

@item Hunspell
@uref{http://hunspell.sourceforge.net/}

@end table

@node Emacs/W3
@section Emacs/W3 --- A World Wide Web browser inside of Emacs
@cindex WWW browser
@cindex Web browser
@cindex HTML browser in Emacs
@cindex @code{w3-mode}

@uref{http://www.gnu.org/software/w3/, Emacs/W3}

@node EDB
@section EDB --- Database program for Emacs; replaces forms editing modes
@cindex EDB
@cindex Database
@cindex Forms mode

@uref{http://gnuvola.org/software/edb/, The Emacs Database}

@node JDEE
@section JDEE --- Integrated development environment for Java
@cindex Java development environment
@cindex Integrated Java development environment
@cindex JDEE

@uref{http://jdee.sourceforge.net/, A Java Development Environment for Emacs}

@c ------------------------------------------------------------
@node Key bindings
@chapter Key bindings
@cindex Key bindings

@menu
* Binding keys to commands::
* Invalid prefix characters::
* Terminal setup code works after Emacs has begun::
* Working with function and arrow keys::
* X key translations for Emacs::
* Backspace invokes help::
* Swapping keys::
* Producing C-XXX with the keyboard::
* No Meta key::
* No Escape key::
* Compose Character::
* Binding combinations of modifiers and function keys::
* Meta key does not work in xterm::
* ExtendChar key does not work as Meta::
* SPC no longer completes file names::
@end menu

@node Binding keys to commands
@section How do I bind keys (including function keys) to commands?
@cindex Binding keys to commands
@cindex Keys, binding to commands
@cindex Commands, binding keys to

Keys can be bound to commands either interactively or in your
@file{.emacs} file.  To interactively bind keys for all modes, type
@kbd{M-x global-set-key @key{RET} @var{key} @var{cmd} @key{RET}}.

To bind a key just in the current major mode, type @kbd{M-x
local-set-key @key{RET} @var{key} @var{cmd} @key{RET}}.

@inforef{Key Bindings, Key Bindings, emacs}, for further details.

To make the process of binding keys interactively easier, use the
following ``trick'': First bind the key interactively, then immediately
type @kbd{C-x @key{ESC} @key{ESC} C-a C-k C-g}.  Now, the command needed
to bind the key is in the kill ring, and can be yanked into your
@file{.emacs} file.  If the key binding is global, no changes to the
command are required.  For example,

@lisp
(global-set-key (quote [f1]) (quote help-for-help))
@end lisp

@noindent
can be placed directly into the @file{.emacs} file.  If the key binding is
local, the command is used in conjunction with the @samp{add-hook} function.
For example, in TeX mode, a local binding might be

@lisp
(add-hook 'tex-mode-hook
  (lambda ()
   (local-set-key (quote [f1]) (quote help-for-help))))
@end lisp


@itemize @bullet

@item
Control characters in key sequences, in the form yanked from the kill
ring are given in their graphic form---i.e., @key{CTRL} is shown as
@samp{^}, @key{TAB} as a set of spaces (usually 8), etc.  You may want
to convert these into their vector or string forms.

@item
If a prefix key of the character sequence to be bound is already
bound as a complete key, then you must unbind it before the new
binding.  For example, if @kbd{ESC @{} is previously bound:

@lisp
(global-unset-key [?\e ?@{])   ;;   or
(local-unset-key [?\e ?@{])
@end lisp

@item
Aside from commands and ``lambda lists,'' a vector or string also
can be bound to a key and thus treated as a macro.  For example:

@lisp
(global-set-key [f10] [?\C-x?\e?\e?\C-a?\C-k?\C-g])  ;;  or
(global-set-key [f10] "\C-x\e\e\C-a\C-k\C-g")
@end lisp

@end itemize

@node Invalid prefix characters
@section Why does Emacs say @samp{Key sequence XXX uses invalid prefix characters}?
@cindex Prefix characters, invalid
@cindex Invalid prefix characters
@cindex Misspecified key sequences

Usually, one of two things has happened.  In one case, the control
character in the key sequence has been misspecified (e.g. @samp{C-f}
used instead of @samp{\C-f} within a Lisp expression).  In the other
case, a @dfn{prefix key} in the keystroke sequence you were trying to bind
was already bound as a @dfn{complete key}.  Historically, the @samp{ESC [}
prefix was usually the problem, in which case you should evaluate either
of these forms before attempting to bind the key sequence:

@lisp
(global-unset-key [?\e ?[])  ;;  or
(global-unset-key "\e[")
@end lisp

@node Terminal setup code works after Emacs has begun
@section Why doesn't this [terminal or window-system setup] code work in my @file{.emacs} file, but it works just fine after Emacs starts up?
@cindex Terminal setup code in @file{.emacs}

During startup, Emacs initializes itself according to a given code/file
order.  If some of the code executed in your @file{.emacs} file needs to
be postponed until the initial terminal or window-system setup code has
been executed but is not, then you will experience this problem (this
code/file execution order is not enforced after startup).

To postpone the execution of Emacs Lisp code until after terminal or
window-system setup, treat the code as a @dfn{lambda list} and set the
value of either the @code{term-setup-hook} or @code{window-setup-hook}
variable to this lambda function.  For example,

@lisp
(add-hook 'term-setup-hook
          (lambda ()
           (when (string-match "\\`vt220" (or (getenv "TERM") ""))
             ;; Make vt220's "Do" key behave like M-x:
             (global-set-key [do] 'execute-extended-command))))
@end lisp

For information on what Emacs does every time it is started, see the
@file{lisp/startup.el} file.

@node Working with function and arrow keys
@section How do I tell what characters or symbols my function or arrow keys emit?
@cindex Working with arrow keys
@cindex Arrow keys, symbols generated by
@cindex Working with function keys
@cindex Function keys, symbols generated by
@cindex Symbols generated by function keys

Type @kbd{C-h c} then the function or arrow keys.  The command will
return either a function key symbol or character sequence (see the
Emacs documentation for an explanation).  This works for other
keys as well.

@node X key translations for Emacs
@section How do I set the X key ``translations'' for Emacs?
@cindex X key translations
@cindex Key translations under X
@cindex Translations for keys under X

Emacs is not written using the Xt library by default, so there are no
``translations'' to be set.  (We aren't sure how to set such translations
if you do build Emacs with Xt; please let us know if you've done this!)

The only way to affect the behavior of keys within Emacs is through
@code{xmodmap} (outside Emacs) or @code{define-key} (inside Emacs).  The
@code{define-key} command should be used in conjunction with the
@code{function-key-map} map.  For instance,

@lisp
(define-key function-key-map [M-@key{TAB}] [?\M-\t])
@end lisp

@noindent
defines the @kbd{M-@key{TAB}} key sequence.

@node Backspace invokes help
@section Why does the @key{Backspace} key invoke help?
@cindex Backspace key invokes help
@cindex Help invoked by Backspace
@cindex DEL key does not delete

The @key{Backspace} key (on most keyboards) generates @acronym{ASCII} code 8.
@kbd{C-h} sends the same code.  In Emacs by default @kbd{C-h} invokes
help-command.  This is intended to be easy to remember since the first
letter of @samp{help} is @samp{h}.  The easiest solution to this problem
is to use @kbd{C-h} (and @key{Backspace}) for help and @key{DEL} (the
@key{Delete} key) for deleting the previous character.

For many people this solution may be problematic:

@itemize @bullet

@item
They normally use @key{Backspace} outside of Emacs for deleting the
previous character.  This can be solved by making @key{DEL} the command
for deleting the previous character outside of Emacs.  On many Unix
systems, this command will remap @key{DEL}:

@example
stty erase `^?'
@end example

@item
The user may prefer the @key{Backspace} key for deleting the
previous character because it is more conveniently located on their
keyboard or because they don't even have a separate @key{Delete} key.
In this case, the @key{Backspace} key should be made to behave like
@key{Delete}.  There are several methods.

@itemize @minus
@item
Some terminals (e.g., VT3## terminals) and terminal emulators (e.g.,
TeraTerm) allow the character generated by the @key{Backspace} key to be
changed from a setup menu.

@item
You may be able to get a keyboard that is completely programmable, or a
terminal emulator that supports remapping of any key to any other key.

@item
With Emacs 21.1 and later, you can control the effect of the
@key{Backspace} and @key{Delete} keys, on both dumb terminals and a
windowed displays, by customizing the option
@code{normal-erase-is-backspace-mode}, or by invoking @kbd{M-x
normal-erase-is-backspace}.  See the documentation of these symbols
(@pxref{Emacs Lisp documentation}) for more info.

@item
It is possible to swap the @key{Backspace} and @key{DEL} keys inside
Emacs:

@lisp
(keyboard-translate ?\C-h ?\C-?)
@end lisp

@noindent
This is the recommended method of forcing @key{Backspace} to act as
@key{DEL}, because it works even in modes which bind @key{DEL} to
something other than @code{delete-backward-char}.

Similarly, you could remap @key{DEL} to act as @kbd{C-d}, which by
default deletes forward:

@lisp
(keyboard-translate ?\C-? ?\C-d)
@end lisp

@xref{Swapping keys}, for further details about @code{keyboard-translate}.

@item
Another approach is to switch key bindings and put help on @kbd{C-x h}
instead:

@lisp
(global-set-key "\C-h" 'delete-backward-char)

;; overrides mark-whole-buffer
(global-set-key "\C-xh" 'help-command)
@end lisp

@noindent
This method is not recommended, though: it only solves the problem for
those modes which bind @key{DEL} to @code{delete-backward-char}.  Modes
which bind @key{DEL} to something else, such as @code{view-mode}, will
not work as you expect when you press the @key{Backspace} key.  For this
reason, we recommend the @code{keyboard-translate} method, shown
above.

Other popular key bindings for help are @kbd{M-?} and @kbd{C-x ?}.
@end itemize

Don't try to bind @key{DEL} to @code{help-command}, because there are
many modes that have local bindings of @key{DEL} that will interfere.

@end itemize

When Emacs 21 or later runs on a windowed display, it binds the
@key{Delete} key to a command which deletes the character at point, to
make Emacs more consistent with keyboard operation on these systems.

For more information about troubleshooting this problem, see @ref{DEL
Does Not Delete, , If @key{DEL} Fails to Delete, emacs, The GNU Emacs
Manual}.

@node Swapping keys
@section How do I swap two keys?
@cindex Swapping keys
@cindex Keys, swapping
@cindex @code{keyboard-translate}

You can swap two keys (or key sequences) by using the
@code{keyboard-translate} function.  For example, to turn @kbd{C-h}
into @key{DEL} and @key{DEL} to @kbd{C-h}, use

@lisp
(keyboard-translate ?\C-h ?\C-?)  ; translate `C-h' to DEL
(keyboard-translate ?\C-? ?\C-h)  ; translate DEL to `C-h'.
@end lisp

@noindent
The first key sequence of the pair after the function identifies what is
produced by the keyboard; the second, what is matched for in the
keymaps.

However, in the specific case of @kbd{C-h} and @key{DEL}, you should
toggle @code{normal-erase-is-backspace-mode} instead of calling
@code{keyboard-translate}.  @inforef{DEL Does Not Delete, DEL Does Not Delete,
emacs}.

Keyboard translations are not the same as key bindings in keymaps.
Emacs contains numerous keymaps that apply in different situations, but
there is only one set of keyboard translations, and it applies to every
character that Emacs reads from the terminal.  Keyboard translations
take place at the lowest level of input processing; the keys that are
looked up in keymaps contain the characters that result from keyboard
translation.

@node Producing C-XXX with the keyboard
@section How do I produce C-XXX with my keyboard?
@cindex Producing control characters
@cindex Generating control characters
@cindex Control characters, generating

On terminals (but not under X), some common ``aliases'' are:

@table @asis

@item @kbd{C-2}  or  @kbd{C-@key{SPC}}
@kbd{C-@@}

@item @kbd{C-6}
@kbd{C-^}

@item @kbd{C-7}  or  @kbd{C-S--}
@kbd{C-_}

@item @kbd{C-4}
@kbd{C-\}

@item @kbd{C-5}
@kbd{C-]}

@item @kbd{C-/}
@kbd{C-?}

@end table

Often other aliases exist; use the @kbd{C-h c} command and try
@key{CTRL} with all of the digits on your keyboard to see what gets
generated.  You can also try the @kbd{C-h w} command if you know the
name of the command.

@node No Meta key
@section What if I don't have a @key{Meta} key?
@cindex No @key{Meta} key
@cindex @key{Meta} key, what to do if you lack it

On many keyboards, the @key{Alt} key acts as @key{Meta}, so try it.

Instead of typing @kbd{M-a}, you can type @kbd{@key{ESC} a}.  In fact,
Emacs converts @kbd{M-a} internally into @kbd{@key{ESC} a} anyway
(depending on the value of @code{meta-prefix-char}).  Note that you
press @key{Meta} and @key{a} together, but with @key{ESC}, you press
@key{ESC}, release it, and then press @key{a}.

@node No Escape key
@section What if I don't have an @key{Escape} key?
@cindex No Escape key
@cindex Lacking an Escape key
@cindex Escape key, lacking

Type @kbd{C-[} instead.  This should send @acronym{ASCII} code 27 just like an
Escape key would.  @kbd{C-3} may also work on some terminal (but not
under X).  For many terminals (notably DEC terminals) @key{F11}
generates @key{ESC}.  If not, the following form can be used to bind it:

@lisp
;; F11 is the documented ESC replacement on DEC terminals.
(define-key function-key-map [f11] [?\e])
@end lisp

@node Compose Character
@section Can I make my @key{Compose Character} key behave like a @key{Meta} key?
@cindex @key{Compose Character} key, using as @key{Meta}
@cindex @key{Meta}, using @key{Compose Character} for

On a dumb terminal such as a VT220, no.  It is rumored that certain
VT220 clones could have their @key{Compose} key configured this way.  If
you're using X, you might be able to do this with the @code{xmodmap}
command.

@node Binding combinations of modifiers and function keys
@section How do I bind a combination of modifier key and function key?
@cindex Modifiers and function keys
@cindex Function keys and modifiers
@cindex Binding modifiers and function keys

You can represent modified function keys in vector format by adding
prefixes to the function key symbol.  For example (from the Emacs
documentation):

@lisp
(global-set-key [?\C-x right] 'forward-page)
@end lisp

@noindent
where @samp{?\C-x} is the Lisp character constant for the character @kbd{C-x}.

You can use the modifier keys @key{Control}, @key{Meta}, @key{Hyper},
@key{Super}, @key{Alt}, and @key{Shift} with function keys.  To
represent these modifiers, prepend the strings @samp{C-}, @samp{M-},
@samp{H-}, @samp{s-}, @samp{A-}, and @samp{S-} to the symbol name.  Here
is how to make @kbd{H-M-RIGHT} move forward a word:

@lisp
(global-set-key [H-M-right] 'forward-word)
@end lisp

@itemize @bullet

@item
Not all modifiers are permitted in all situations.  @key{Hyper},
@key{Super}, and @key{Alt} are not available on Unix character
terminals.  Non-@acronym{ASCII} keys and mouse events (e.g. @kbd{C-=} and
@kbd{Mouse-1}) also fall under this category.

@end itemize

@xref{Binding keys to commands}, for general key binding instructions.

@node Meta key does not work in xterm
@section Why doesn't my @key{Meta} key work in an @code{xterm} window?
@cindex @key{Meta} key and @code{xterm}
@cindex Xterm and @key{Meta} key

@inforef{Unibyte Mode, Single-Byte Character Set Support, emacs}.

If the advice in the Emacs manual fails, try all of these methods before
asking for further help:

@itemize @bullet

@item
You may have big problems using @code{mwm} as your window manager.
(Does anyone know a good generic solution to allow the use of the
@key{Meta} key in Emacs with @file{mwm}?)

@item
For X11: Make sure it really is a @key{Meta} key.  Use @code{xev} to
find out what keysym your @key{Meta} key generates.  It should be either
@code{Meta_L} or @code{Meta_R}.  If it isn't, use @file{xmodmap} to fix
the situation.  If @key{Meta} does generate @code{Meta_L} or
@code{Meta_R}, but @kbd{M-x} produces a non-@acronym{ASCII} character, put this in
your @file{~/.Xdefaults} file:

@example
 XTerm*eightBitInput:   false
 XTerm*eightBitOutput:  true
@end example

@item
Make sure the @code{pty} the @code{xterm} is using is passing 8 bit
characters.  @samp{stty -a} (or @samp{stty everything}) should show
@samp{cs8} somewhere.  If it shows @samp{cs7} instead, use @samp{stty
cs8 -istrip} (or @samp{stty pass8}) to fix it.

@item
If there is an @code{rlogin} connection between @code{xterm} and Emacs, the
@samp{-8} argument may need to be given to rlogin to make it pass all 8 bits
of every character.

@item
If Emacs is running on Ultrix, it is reported that evaluating
@code{(set-input-mode t nil)} helps.

@item
If all else fails, you can make @code{xterm} generate @kbd{@key{ESC} W} when
you type @kbd{M-W}, which is the same conversion Emacs would make if it
got the @kbd{M-W} anyway.  In X11R4, the following resource
specification will do this:

@example
XTerm.VT100.EightBitInput: false
@end example

@noindent
(This changes the behavior of the @code{insert-eight-bit} action.)

With older @code{xterm}s, you can specify this behavior with a translation:

@example
XTerm.VT100.Translations: #override \
  Meta<KeyPress>: string(0x1b) insert()
@end example

@noindent
You might have to replace @samp{Meta} with @samp{Alt}.

@end itemize

@node ExtendChar key does not work as Meta
@section Why doesn't my @key{ExtendChar} key work as a @key{Meta} key under HP-UX 8.0 and 9.x?
@cindex @key{ExtendChar} key as @key{Meta}
@cindex @key{Meta}, using @key{ExtendChar} for
@cindex HP-UX, the @key{ExtendChar} key

This is a result of an internationalization extension in X11R4 and the
fact that HP is now using this extension.  Emacs assumes that the
@code{XLookupString} function returns the same result regardless of the
@key{Meta} key state which is no longer necessarily true.  Until Emacs
is fixed, the temporary kludge is to run this command after each time
the X server is started but preferably before any xterm clients are:

@example
xmodmap -e 'remove mod1 = Mode_switch'
@end example

@c FIXME: Emacs 21 supports I18N in X11; does that mean that this bug is
@c solved?

This will disable the use of the extra keysyms systemwide, which may be
undesirable if you actually intend to use them.

@node SPC no longer completes file names
@section Why doesn't SPC complete file names anymore?
@cindex @kbd{SPC} file name completion

Starting with Emacs 22.1, @kbd{SPC} no longer completes file names in
the minibuffer, so that file names with embedded spaces could be typed
without the need to quote the spaces.

You can get the old behavior by binding @kbd{SPC} to
@code{minibuffer-complete-word} in the minibuffer, as follows:

@lisp
(define-key minibuffer-local-filename-completion-map (kbd "SPC")
  'minibuffer-complete-word)

(define-key minibuffer-local-must-match-filename-map (kbd "SPC")
  'minibuffer-complete-word)
@end lisp

@c ------------------------------------------------------------
@node Alternate character sets
@chapter Alternate character sets
@cindex Alternate character sets

@menu
* Emacs does not display 8-bit characters::
* Inputting eight-bit characters::
* Right-to-left alphabets::
* How to add fonts::
@end menu

@node Emacs does not display 8-bit characters
@section How do I make Emacs display 8-bit characters?
@cindex Displaying eight-bit characters
@cindex Eight-bit characters, displaying

@inforef{Unibyte Mode, Single-byte Character Set
Support, emacs}.  On a Unix, when Emacs runs on a text-only terminal
display or is invoked with @samp{emacs -nw}, you typically need to use
@code{set-terminal-coding-system} to tell Emacs what the terminal can
display, even after setting the language environment; otherwise
non-@acronym{ASCII} characters will display as @samp{?}.  On other operating
systems, such as MS-DOS and MS-Windows, Emacs queries the OS about the
character set supported by the display, and sets up the required
terminal coding system automatically.

@node Inputting eight-bit characters
@section How do I input eight-bit characters?
@cindex Entering eight-bit characters
@cindex Eight-bit characters, entering
@cindex Input, 8-bit characters

Various methods are available for input of eight-bit characters.  See
@inforef{Unibyte Mode, Single-byte Character Set
Support, emacs}.  For more sophisticated methods, @inforef{Input
Methods, Input Methods, emacs}.

@node Right-to-left alphabets
@section Where is an Emacs that can handle Semitic (right-to-left) alphabets?
@cindex Right-to-left alphabets
@cindex Hebrew, handling with Emacs
@cindex Semitic alphabets
@cindex Arabic alphabets
@cindex Bidirectional text

Emacs supports Hebrew characters (ISO 8859-8) since version 20, but does
not yet support right-to-left character entry and display.  The
@uref{http://lists.gnu.org/mailman/listinfo/emacs-bidi, emacs-bidi
mailing list} discusses development of support for this feature.


@node How to add fonts
@section How do I add fonts for use with Emacs?
@cindex add fonts for use with Emacs
@cindex intlfonts

First, download and install the BDF font files and any auxiliary
packages they need.  The GNU Intlfonts distribution can be found on
@uref{http://directory.fsf.org/localization/intlfonts.html, the GNU
Software Directory Web site}.

Next, if you are on X Window system, issue the following two commands
from the shell's prompt:

@example
  xset +fp /usr/local/share/emacs/fonts
  xset fp rehash
@end example

@noindent
(Modify the first command if you installed the fonts in a directory
that is not @file{/usr/local/share/emacs/fonts}.)  You also need to
arrange for these two commands to run whenever you log in, e.g., by
adding them to your window-system startup file, such as
@file{~/.xsessionrc} or @file{~/.gnomerc}.

Now, add the following line to your @file{~/.emacs} init file:

@lisp
  (add-to-list 'bdf-directory-list "/usr/share/emacs/fonts/bdf")
@end lisp

@noindent
(Again, modify the file name if you installed the fonts elsewhere.)

Finally, if you wish to use the installed fonts with @code{ps-print},
add the following line to your @file{~/.emacs}:

@lisp
  (setq ps-multibyte-buffer 'bdf-font-except-latin)
@end lisp

A few additional steps are necessary for MS-Windows; they are listed
below.

First, make sure @emph{all} the directories with BDF font files are
mentioned in @code{bdf-directory-list}.  On Unix and GNU/Linux
systems, one normally runs @kbd{make install} to install the BDF fonts
in the same directory.  By contrast, Windows users typically don't run
the Intlfonts installation command, but unpack the distribution in
some directory, which leaves the BDF fonts in its subdirectories.  For
example, assume that you unpacked Intlfonts in @file{C:/Intlfonts};
then you should set @code{bdf-directory-list} as follows:

@lisp
  (setq bdf-directory-list
    '("C:/Intlfonts/Asian"
      "C:/Intlfonts/Chinese" "C:/Intlfonts/Chinese.X"
      "C:/Intlfonts/Chinese.BIG" "C:/Intlfonts/Ethiopic"
      "C:/Intlfonts/European" "C:/Intlfonts/European.BIG"
      "C:/Intlfonts/Japanese" "C:/Intlfonts/Japanese.X"
      "C:/Intlfonts/Japanese.BIG" "C:/Intlfonts/Korean.X"
      "C:/Intlfonts/Misc"))
@end lisp

@cindex @code{w32-bdf-filename-alist}
@cindex @code{w32-find-bdf-fonts}
Next, you need to set up the variable @code{w32-bdf-filename-alist} to
an alist of the BDF fonts and their corresponding file names.
Assuming you have set @code{bdf-directory-list} to name all the
directories with the BDF font files, the following Lisp snippet will
set up @code{w32-bdf-filename-alist}:

@lisp
  (setq w32-bdf-filename-alist
     (w32-find-bdf-fonts bdf-directory-list))
@end lisp

Now, create fontsets for the BDF fonts:

@lisp
  (create-fontset-from-fontset-spec
   "-*-fixed-medium-r-normal-*-16-*-*-*-c-*-fontset-bdf,
   japanese-jisx0208:-*-*-medium-r-normal-*-16-*-*-*-c-*-jisx0208.1983-*,
   katakana-jisx0201:-*-*-medium-r-normal-*-16-*-*-*-c-*-jisx0201*-*,
   latin-jisx0201:-*-*-medium-r-normal-*-16-*-*-*-c-*-jisx0201*-*,
   japanese-jisx0208-1978:-*-*-medium-r-normal-*-16-*-*-*-c-*-jisx0208.1978-*,
   thai-tis620:-misc-fixed-medium-r-normal--16-160-72-72-m-80-tis620.2529-1,
   lao:-misc-fixed-medium-r-normal--16-160-72-72-m-80-MuleLao-1,
   tibetan-1-column:-TibMdXA-fixed-medium-r-normal--16-160-72-72-m-80-MuleTibetan-1,
   ethiopic:-Admas-Ethiomx16f-Medium-R-Normal--16-150-100-100-M-160-Ethiopic-Unicode,
   tibetan:-TibMdXA-fixed-medium-r-normal--16-160-72-72-m-160-MuleTibetan-0")
@end lisp

Many of the international bdf fonts from Intlfonts are type 0, and
therefore need to be added to font-encoding-alist:

@lisp
  (setq font-encoding-alist
        (append '(("MuleTibetan-0" (tibetan . 0))
                  ("GB2312"        (chinese-gb2312 . 0))
                  ("JISX0208"      (japanese-jisx0208 . 0))
                  ("JISX0212"      (japanese-jisx0212 . 0))
                  ("VISCII"        (vietnamese-viscii-lower . 0))
                  ("KSC5601"       (korean-ksc5601 . 0))
                  ("MuleArabic-0"  (arabic-digit . 0))
                  ("MuleArabic-1"  (arabic-1-column . 0))
                  ("MuleArabic-2"  (arabic-2-column . 0)))
                font-encoding-alist))
@end lisp

You can now use the Emacs font menu to select the @samp{bdf: 16-dot medium}
fontset, or you can select it by setting the default font in your
@file{~/.emacs}:

@lisp
  (set-default-font "fontset-bdf")
@end lisp


@c ------------------------------------------------------------
@node Mail and news
@chapter Mail and news
@cindex Mail and news

@menu
* Changing the included text prefix::
* Saving a copy of outgoing mail::
* Expanding aliases when sending mail::
* Sorting the messages in an Rmail folder::
* Rmail writes to /var/spool/mail::
* Replying to the sender of a message::
* Automatically starting a mail or news reader::
* Reading news with Emacs::
* Gnus does not work with NNTP::
* Making Gnus faster::
* Catching up in all newsgroups::
@end menu

@node Changing the included text prefix
@section How do I change the included text prefix in mail/news followups?
@cindex Prefix in mail/news followups, changing
@cindex Included text prefix, changing
@cindex Setting the included text character
@cindex Quoting in mail messages

If you read mail with Rmail, set the variable @code{mail-yank-prefix}.
For Gnus, set @code{message-yank-prefix}.  For VM, set
@code{vm-included-text-prefix}.  For mh-e, set @code{mh-ins-buf-prefix}.

For fancier control of citations, use Supercite (@pxref{Top,, the Supercite
Manual, sc, The Supercite Manual}).

To prevent Emacs from including various headers of the replied-to
message, set the value of @code{mail-yank-ignored-headers} to an
appropriate regexp.

@node Saving a copy of outgoing mail
@section How do I save a copy of outgoing mail?
@cindex Saving a copy of outgoing mail
@cindex Copying outgoing mail to a file
@cindex Filing outgoing mail
@cindex Automatic filing of outgoing mail
@cindex Mail, saving outgoing automatically

You can either mail yourself a copy by including a @samp{BCC} header in the
mail message, or store a copy of the message directly to a file by
including an @samp{FCC} header.

If you use standard mail, you can automatically create a @samp{BCC} to
yourself by putting

@lisp
(setq mail-self-blind t)
@end lisp

@noindent
in your @file{.emacs} file.  You can automatically include an @samp{FCC}
field by putting something like the following in your @file{.emacs}
file:

@lisp
(setq mail-archive-file-name (expand-file-name "~/outgoing"))
@end lisp

The output file will be in Unix mail format.

If you use @code{mh-e}, add an @samp{FCC} or @samp{BCC} field to your
components file.

It does not work to put @samp{set record filename} in the @file{.mailrc}
file.

@node Expanding aliases when sending mail
@section Why doesn't Emacs expand my aliases when sending mail?
@cindex Expanding aliases when sending mail
@cindex Mail alias expansion
@cindex Sending mail with aliases

@xref{Mail Aliases,, The Emacs Manual, emacs, The Emacs Manual}.

@itemize @bullet

@item
Normally, Emacs expands aliases when you send the message.
To expand them before this, use @kbd{M-x expand-mail-aliases}.

@item
Emacs normally only reads the @file{.mailrc} file once per session, when
you start to compose your first mail message.  If you edit the file
after this, you can use @kbd{M-x build-mail-aliases} to make Emacs
reread it.  Prior to Emacs 24.1, this is not an interactive command, so
you must instead type @kbd{M-: (build-mail-aliases) @key{RET}}.

@item
If you like, you can expand mail aliases as abbrevs, as soon as you
type them in.  To enable this feature, execute the following:

@lisp
(add-hook 'mail-mode-hook 'mail-abbrevs-setup)
@end lisp

Note that the aliases are expanded automatically only after you type
a word-separator character (e.g. @key{RET} or @kbd{,}).  You can force their
expansion by moving point to the end of the alias and typing @kbd{C-x a e}
(@kbd{M-x expand-abbrev}).
@end itemize

@node Sorting the messages in an Rmail folder
@section How can I sort the messages in my Rmail folder?
@cindex Rmail, sorting messages in
@cindex Folder, sorting messages in an Rmail
@cindex Sorting messages in an Rmail folder

In Rmail, type @kbd{C-c C-s C-h} to get a list of sorting functions
and their key bindings.

@node Rmail writes to /var/spool/mail
@section Why does Rmail need to write to @file{/var/spool/mail}?
@cindex Rmail and @file{/var/spool/mail}
@cindex @file{/var/spool/mail} and Rmail

This is the behavior of the @code{movemail} program which Rmail uses.
This indicates that @code{movemail} is configured to use lock files.

RMS writes:

@quotation
Certain systems require lock files to interlock access to mail files.
On these systems, @code{movemail} must write lock files, or you risk losing
mail.  You simply must arrange to let @code{movemail} write them.

Other systems use the @code{flock} system call to interlock access.  On
these systems, you should configure @code{movemail} to use @code{flock}.
@end quotation

@node Replying to the sender of a message
@section How can I force Rmail to reply to the sender of a message, but not the other recipients?
@cindex Replying only to the sender of a message
@cindex Sender, replying only to
@cindex Rmail, replying to the sender of a message in

@email{isaacson@@seas.upenn.edu, Ron Isaacson} says: When you hit
@key{r} to reply in Rmail, by default it CCs all of the original
recipients (everyone on the original @samp{To} and @samp{CC}
lists). With a prefix argument (i.e., typing @kbd{C-u} before @key{r}),
it replies only to the sender.  However, going through the whole
@kbd{C-u} business every time you want to reply is a pain.  This is the
best fix I've been able to come up with:

@lisp
(defun rmail-reply-t ()
  "Reply only to the sender of the current message. (See rmail-reply.)"
  (interactive)
  (rmail-reply t))

(add-hook 'rmail-mode-hook
  (lambda ()
    (define-key rmail-mode-map "r" 'rmail-reply-t)
    (define-key rmail-mode-map "R" 'rmail-reply)))
@end lisp

@node Automatically starting a mail or news reader
@section How do I make Emacs automatically start my mail/news reader?
@cindex Mail reader, starting automatically
@cindex News reader, starting automatically
@cindex Starting mail/news reader automatically

To start Emacs in Gnus:

@example
emacs -f gnus
@end example

@noindent
in Rmail:

@example
emacs -f rmail
@end example

A more convenient way to start with Gnus:

@example
alias gnus 'emacs -f gnus'
gnus
@end example

It is probably unwise to automatically start your mail or news reader
from your @file{.emacs} file.  This would cause problems if you needed to run
two copies of Emacs at the same time.  Also, this would make it difficult for
you to start Emacs quickly when you needed to.

@node Reading news with Emacs
@section How do I read news under Emacs?
@cindex Reading news under Emacs
@cindex Usenet reader in Emacs
@cindex Gnus newsreader
@cindex FAQ for Gnus
@cindex Gnus FAQ
@cindex Learning more about Gnus

Use @kbd{M-x gnus}.  For more information on Gnus, @pxref{Top,, the Gnus
Manual, gnus, The Gnus Manual}, which includes @ref{Frequently Asked
Questions,, the Gnus FAQ, gnus}.


@node Gnus does not work with NNTP
@section Why doesn't Gnus work via NNTP?
@cindex Gnus and NNTP
@cindex NNTP, Gnus fails to work with

There is a bug in NNTP version 1.5.10, such that when multiple requests
are sent to the NNTP server, the server only handles the first one
before blocking waiting for more input which never comes.  NNTP version
1.5.11 claims to fix this.

You can work around the bug inside Emacs like this:

@lisp
(setq nntp-maximum-request 1)
@end lisp

You can find out what version of NNTP your news server is running by
telnetting to the NNTP port (usually 119) on the news server machine
(i.e., @kbd{telnet server-machine 119}).  The server should give its
version number in the welcome message.  Type @kbd{quit} to get out.

@node Making Gnus faster
@section How do I make Gnus faster?
@cindex Faster, starting Gnus
@cindex Starting Gnus faster
@cindex Gnus, starting faster
@cindex Slow catch up in Gnus
@cindex Gnus is slow when catching up
@cindex Crosspostings make Gnus catching up slow

From the Gnus FAQ (@pxref{Reading news with Emacs}):

@quotation
If you have a slow machine, or are just really impatient, there are a
few things you can do to make Gnus run faster.

Set @code{gnus-check-new-newsgroups} and
@code{gnus-check-bogus-newsgroups} to @code{nil} to make startup faster.

Set @code{gnus-show-threads}, @code{gnus-use-cross-reference} and
@code{gnus-nov-is-evil} to @code{nil} to make entering and exiting the
summary buffer faster.
@end quotation

@node Catching up in all newsgroups
@section How do I catch up all newsgroups in Gnus?
@cindex Catching up all newsgroups in Gnus
@cindex Gnus, Catching up all newsgroups in

In the @file{*Newsgroup*} buffer, type @kbd{M-< C-x ( c y C-x ) M-0 C-x e}

Leave off the initial @kbd{M-<} if you only want to catch up from point
to the end of the @file{*Newsgroup*} buffer.

@node Concept index
@unnumbered Concept Index
@printindex cp

@bye