doc/en/utf-8.xml

<?xml version='1.0' encoding="UTF-8"?>
<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/utf-8.xml,v 1.9 2005/04/05 08:59:28 neysx Exp $ -->
<!DOCTYPE guide SYSTEM "/dtd/guide.dtd">

<guide link="/doc/en/utf-8.xml">
<title>Using UTF-8 with Gentoo</title>

<author title="Author">
  <mail link="slarti@gentoo.org">Thomas Martin</mail>
</author>
<author title="Contributor">
  <mail link="devil@gentoo.org.ua">Alexander Simonov</mail>
</author>

<abstract>
This guide shows you how to set up and use the UTF-8 Unicode character set with
your Gentoo Linux system, after explaining the benefits of Unicode and more
specifically UTF-8.
</abstract>

<license />

<version>1.8</version>
<date>2005-04-05</date>

<chapter>
<title>Character Encodings</title>
<section>
<title>What is a Character Encoding?</title>
<body>

<p>
Computers do not understand text themselves. Instead, every character is
represented by a number. Traditionally, each set of numbers used to represent
alphabets and characters (known as a coding system, encoding or character set)
was limited in size due to limitations in computer hardware.
</p>

</body>
</section>
<section>
<title>The History of Character Encodings</title>
<body>

<p>
The most common (or at least the most widely accepted) character set is
<b>ASCII</b> (American Standard Code for Information Interchange). It is widely
held that ASCII is the most successful software standard ever.  Modern ASCII
was standardised in 1986 (ANSI X3.4, RFC 20, ISO/IEC 646:1991, ECMA-6) by the
American National Standards Institute.
</p>

<p>
ASCII is strictly seven-bit, meaning that it uses bit patterns representable
with seven binary digits, which provides a range of 0 to 127 in decimal. These
include 32 non-visible control characters, most between 0 and 31, with the
final control character, DEL or delete at 127.  Characters 32 to 126 are
visible characters: a space, punctuation marks, Latin letters and numbers.
</p>

<p>
The eighth bit in ASCII was originally used as a parity bit for error checking.
If this is not desired, it is left as 0. This means that, with ASCII, each
character is represented by a single byte.
</p>

<p>
Although ASCII was enough for communication in modern English, in other
European languages that include accented characters, things were not so easy.
The ISO 8859 standards were developed to meet these needs.  They were backwards
compatible with ASCII, but instead of leaving the eighth bit blank, they used
it to allow another 127 characters in each encoding. ISO 8859's limitations
soon came to light, and there are currently 15 variants of the ISO 8859
standard (8859-1 through to 8859-15).  Outside of the ASCII-compatible byte
range of these character sets, there is often conflict between the letters
represented by each byte. To complicate interoperability between character
encodings further, Windows-1252 is used in some versions of Microsoft Windows
instead for Western European languages. This is a superset of ISO 8859-1,
however it is different in several ways. These sets do all retain ASCII
compatibility, however.
</p>

<p>
The necessary development of completely different single-byte encodings for
non-Latin alphabets, such as EUC (Extended Unix Coding) which is used for
Japanese and Korean (and to a lesser extent Chinese) created more confusion,
while other operating systems still used different character sets for the same
languages, for example, Shift-JIS and ISO-2022-JP.  Users wishing to view
cyrillic glyphs had to choose between KOI8-R for Russian and Bulgarian or
KOI8-U for Ukrainian, as well as all the other cyrillic encodings such as the
unsuccessful ISO 8859-5, and the common Windows-1251 set. All of these
character sets broke most compatibility with ASCII (although KOI8 encodings
place cyrillic characters in Latin order, so in case the eighth bit is
stripped, text is still decipherable on an ASCII terminal through case-reversed
transliteration.)
</p>

<p>
This has led to confusion, and also to an almost total inability for
multilingual communication, especially across different alphabets. Enter
Unicode.
</p>

</body>
</section>
<section>
<title>What is Unicode?</title>
<body>

<p>
Unicode throws away the traditional single-byte limit of character sets.  It
uses 17 "planes" of 65,536 code points to describe a maximum of 1,114,112
characters. As the first plane, aka. "Basic Multilingual Plane" or BMP,
contains almost everything you will ever use, many have made the wrong
assumption that Unicode was a 16-bit character set.
</p>

<p>
Unicode has been mapped in many different ways, but the two most common are
<b>UTF</b> (Unicode Transformation Format) and <b>UCS</b> (Universal Character
Set). A number after UTF indicates the number of bits in one unit, while the
number after UCS indicates the number of bytes. UTF-8 has become the most
widespread means for the interchange of Unicode text as a result of its
eight-bit clean nature, and it is the subject of this document.
</p>

</body>
</section>
<section>
<title>UTF-8</title>
<body>

<p>
UTF-8 is a variable-length character encoding, which in this instance means
that it uses 1 to 4 bytes per symbol. So, the first UTF-8 byte is used for
encoding ASCII, giving the character set full backwards compatibility with
ASCII. UTF-8 means that ASCII and Latin characters are interchangeable with
little increase in the size of the data, because only the first bit is used.
Users of Eastern alphabets such as Japanese, who have been assigned a higher
byte range are unhappy, as this results in as much as a 50% redundancy in their
data.
</p>

</body>
</section>
<section>
<title>What UTF-8 Can Do for You</title>
<body>

<p>
UTF-8 allows you to work in a standards-compliant and internationally accepted
multilingual environment, with a comparatively low data redundancy. UTF-8 is
the preferred way for transmitting non-ASCII characters over the Internet,
through Email, IRC or almost any other medium. Despite this, many people regard
UTF-8 in online communication as abusive. It is always best to be aware of the
attitude towards UTF-8 in a specific channel, mailing list or Usenet group
before using <e>non-ASCII</e> UTF-8.
</p>

</body>
</section>
</chapter>

<chapter>
<title>Setting up UTF-8 with Gentoo Linux</title>
<section>
<title>Finding or Creating UTF-8 Locales</title>
<body>

<p>
Now that you understand the principles behind Unicode, you're ready to start
using UTF-8 with your system.
</p>

<p>
The preliminary requirement for UTF-8 is to have a version of glibc installed
that has national language support. The recommend means to do this is the
<path>/etc/locales.build</path> file in combination with the <c>userlocales</c>
USE flag. It is beyond the scope of this document to explain the usage of this
file though, luckily, the usage of this file is well documented in the comments
within it. It is also explained in the <uri
link="/doc/en/guide-localization.xml#doc_chap3_sect3"> Gentoo Localisation
Guide</uri>.
</p>

<p>
Next, we'll need to decide whether a UTF-8 locale is already available for our
language, or whether we need to create one.
</p>

<pre caption="Checking for an existing UTF-8 locale">
<comment>(Replace "en_GB" with your desired locale setting)</comment>
# <i>locale -a | grep 'en_GB'</i>
en_GB
en_GB.utf8
</pre>

<p>
From the output of this command line, we need to take the result with a suffix
similar to <c>.utf8</c>. If there is no result with a suffix similar to
<c>.utf8</c>, we need to create a UTF-8 compatible locale.
</p>

<note>
Only execute the following code listing if you do not have a UTF-8 locale
available for your language.
</note>

<pre caption="Creating a UTF-8 locale">
<comment>(Replace "en_GB" with your desired locale setting)</comment>
# <i>localedef -i en_GB -f UTF-8 en_GB.utf8</i>
</pre>

<p>
Another way to include a UTF-8 locale is to add it to the
<path>/etc/locales.build</path> file and rebuild <c>glibc</c> with the
<c>userlocales</c> USE flag set.
</p>

<pre caption="Line in /etc/locales.build">
en_GB.UTF-8/UTF-8
</pre>

</body>
</section>
<section>
<title>Setting the Locale</title>
<body>

<p>
Although by now you might be determined to use UTF-8 system wide, the author
does not recommend setting UTF-8 for the root user. Instead, it is best to set
the locale in your user's <path>~/.profile</path> (or, if you are using a C
shell, <path>~/.login</path>).
</p>

<note>
If you are not sure which file to use, use <path>~/.profile</path>.  Also, if
you are unsure which code listing to use, use the Bourne version.
</note>

<pre caption="Setting the locale with environment variables (Bourne version)">
export LANG="en_GB.utf8"
export LC_ALL="en_GB.utf8"
</pre>

<pre caption="Setting the locale with environment variables (C shell version)">
setenv LANG "en_GB.utf8"
setenv LC_ALL "en_GB.utf8"
</pre>

<p>
Now, logout and back in to apply the change. We want these environment
variables in our entire environment, so it is best to logout and back in, or at
the very least to source <path>~/.profile</path> or <path>~/.login</path> in
the console from which you have started other processes.
</p>

</body>
</section>
</chapter>

<chapter>
<title>Application Support</title>
<section>
<body>

<p>
When Unicode first started gaining momentum in the software world, multibyte
character sets were not well suited to languages like C, in which many of the
day-to-day programs people use are written.  Even today, some programs are not
able to handle UTF-8 properly.  Fortunately, most are!
</p>

</body>
</section>
<section>
<title>Filenames, NTFS, and FAT</title>
<body>

<p>
There are several NLS options in the Linux kernel configuration menu, but it is
important to not become confused! For the most part, the only thing you need to
do is to build UTF-8 NLS support into your kernel, and change the default NLS
option to utf8.
</p>

<pre caption="Kernel configuration steps for UTF-8 NLS">
File Systems --&gt;
  Native Language Support --&gt;
    (utf8) Default NLS Option
    &lt;*&gt; NLS UTF8
    <comment>(Also &lt;*&gt; other character sets that are in use in
    your FAT filesystems or Joilet CD-ROMs.)</comment>
</pre>

<p>
If you plan on mounting NTFS partitions, you may need to specify an <c>nls=</c>
option with mount. For more information, see <c>man mount</c>.
</p>

<p>
For changing the encoding of filenames, <c>app-text/convmv</c> can be used.
</p>

<pre caption="Example usage of convmv">
# <i>emerge --ask app-text/convmv</i>
# <i>convmv -f current-encoding -t utf-8 filename</i>
</pre>

<p>
For changing the <e>contents</e> of files, use the <c>iconv</c> utility,
bundled with <c>glibc</c>:
</p>

<pre caption="Example usage of iconv">
<comment>(substitute iso-8859-1 with the charset you are converting from)</comment>
<comment>(Check the output is sane)</comment>
# <i>iconv -f iso-8859-1 -t utf-8 filename</i> 
<comment>(Convert a file, you must create another file)</comment>
# <i>iconv -f iso-8859-1 -t utf-8 filename > newfile</i>
</pre>

<p>
<c>app-text/recode</c> can also be used for this purpose.
</p>

</body>
</section>
<section>
<title>The System Console</title>
<body>

<impo>
You need >=sys-apps/baselayout-1.11.9 for Unicode on the console.
</impo>

<p>
To enable UTF-8 on the console, you should edit <path>/etc/rc.conf</path> and
set <c>UNICODE="yes"</c>, and also read the comments in that file -- it is
important to have a font that has a good range of characters if you plan on
making the most of Unicode.
</p>

<p>
The <c>KEYMAP</c> variable, set in <path>/etc/conf.d/keymaps</path>, should
have a Unicode keymap specified. To do this, simply prepend the keymap already
specified there with -u.
</p>

<pre caption="Example /etc/conf.d/keymaps snippet">
<comment>(Change "uk" to your local layout)</comment>
KEYMAP="-u uk"
</pre>

</body>
</section>
<section>
<title>Ncurses and Slang</title>
<body>

<note>
Ignore any mention of Slang in this section if you do not have it installed or
do not use it.
</note>

<p>
It is wise to add <c>unicode</c> to your global USE flags in
<path>/etc/make.conf</path>, and then to remerge <c>sys-libs/ncurses</c> and
also <c>sys-libs/slang</c> if appropriate:
</p>

<pre caption="Emerging ncurses and slang">
<comment>(We avoid putting these libraries in our world file with --oneshot)</comment>
# <i>emerge --oneshot --verbose --ask sys-libs/ncurses sys-libs/slang</i>
</pre>

<p>
We also need to rebuild packages that link to these, now the USE changes have
been applied. The tool we use (<c>revdep-rebuild</c>) is part of the
<c>gentoolkit</c> package.
</p>

<pre caption="Rebuilding of programs that link to ncurses or slang">
# <i>revdep-rebuild --soname libncurses.so.5</i>
# <i>revdep-rebuild --soname libslang.so.1</i>
</pre>

</body>
</section>
<section>
<title>KDE, GNOME and Xfce</title>
<body>

<p>
All of the major desktop environments have full Unicode support, and will
require no further setup than what has already been covered in this guide. This
is because the underlying graphical toolkits (Qt or GTK+2) are UTF-8 aware.
Subsequently, all applications running on top of these toolkits should be
UTF-8-aware out of the box.
</p>

<p>
The exceptions to this rule come in Xlib and GTK+1. GTK+1 requires a
iso-10646-1 FontSpec in the ~/.gtkrc, for example
<c>-misc-fixed-*-*-*-*-*-*-*-*-*-*-iso10646-1</c>. Also, applications using
Xlib or Xaw will need to be given a similar FontSpec, otherwise they will not
work.
</p>

<note>
If you have a version of the gnome1 control center around, use that instead.
Pick any iso10646-1 font from there.
</note>

<pre caption="Example ~/.gtkrc (for GTK+1) that defines a Unicode compatible font">
style "user-font"
{
    fontset="-misc-fixed-*-*-*-*-*-*-*-*-*-*-iso10646-1"
}
widget_class "*" style "user-font"
</pre>

<p>
If an application has support for both a Qt and GTK+2 GUI, the GTK+2 GUI will
generally give better results with Unicode.
</p>

</body>
</section>
<section>
<title>X11 and Fonts</title>
<body>

<impo>
<c>x11-base/xorg-x11</c> has far better support for Unicode than XFree86
and is <e>highly</e> recommended.
</impo>

<p>
TrueType fonts have support for Unicode, and most of the fonts that ship with
Xorg have impressive character support, although, obviously, not every single
glyph available in Unicode has been created for that font. To build fonts
(including the Bitstream Vera set) with support for East Asian letters with X,
make sure you have the <c>cjk</c> USE flag set. Many other applications utilise
this flag, so it may be worthwhile to add it as a permanent USE flag.
</p>

<p>
Also, several font packages in Portage are Unicode aware.
</p>

<pre caption="Optional: Install some more Unicode-aware fonts">
# <i>emerge terminus-font intlfonts freefonts cronyx-fonts corefonts</i>
</pre>

</body>
</section>
<section>
<title>Window Managers and Terminal Emulators</title>
<body>

<p>
Window managers not built on GTK or Qt generally have very good Unicode
support, as they often use the Xft library for handling fonts. If your window
manager does not use Xft for fonts, you can still use the FontSpec mentioned in
the previous section as a Unicode font.
</p>

<p>
Terminal emulators that use Xft and support Unicode are harder to come by.
Aside from Konsole and gnome-terminal, the best options in Portage are
<c>x11-terms/rxvt-unicode</c>, <c>xfce-extra/terminal</c>,
<c>gnustep-apps/terminal</c>, <c>x11-terms/mlterm</c>, <c>x11-terms/mrxvt</c> or
plain <c>x11-terms/xterm</c> when built with the <c>unicode</c> USE flag and
invoked as <c>uxterm</c>.  <c>app-misc/screen</c> supports UTF-8 too, when
invoked as <c>screen -u</c> or the following is put into the
<path>~/.screenrc</path>:
</p>

<pre caption="~/.screenrc for UTF-8">
defutf8 on
</pre>

</body>
</section>
<section>
<title>Vim, Emacs, Xemacs and Nano</title>
<body>

<p>
Vim, Emacs and Xemacs provide full UTF-8 support, and also have builtin
detection of UTF-8 files. For further information in Vim, use <c>:help
mbyte.txt</c>.
</p>

<p>
Nano currently does not provide support for UTF-8, although it has been planned
for a long time. With luck, this will change in future. At the time of writing,
UTF-8 support is in Nano's CVS, and should be included in the next release.
</p>

</body>
</section>
<section>
<title>Shells</title>
<body>

<p>
Currently, <c>bash</c> provides full Unicode support through the GNU readline
library. Z Shell users are in a somewhat worse position -- no parts of the
shell have Unicode support, although there is a concerted effort to add
multibyte character set support underway at the moment.
</p>

<p>
The C shell, <c>tcsh</c> and <c>ksh</c> do not provide UTF-8 support at all.
</p>

</body>
</section>
<section>
<title>Irssi</title>
<body>

<p>
Since 0.8.10, Irssi has complete UTF-8 support, although it does require a user
to set an option.
</p>

<pre caption="Enabling UTF-8 in Irssi">
/set term_charset UTF-8
</pre>

<p>
For channels where non-ASCII characters are often exchanged in non-UTF-8
charsets, the <c>/recode</c> command may be used to convert the characters.
Type <c>/help recode</c> for more information.
</p>

</body>
</section>
<section>
<title>Mutt</title>
<body>

<p>
The Mutt mail user agent has very good Unicode support. To use UTF-8 with Mutt,
put the following in your <path>~/.muttrc</path>:
</p>

<pre caption="~/.muttrc for UTF-8">
set send_charset="utf8" <comment>(outgoing character set)</comment>
set charset="utf8"      <comment>(display character set)</comment>
</pre>

<note>
You may still see '?' in mail you read with Mutt. This is a result of people
using a mail client which does not indicate the used charset. You can't do much
about this than to ask them to configure their client correctly.
</note>

<p>
Further information is available from the <uri
link="http://wiki.mutt.org/index.cgi?MuttFaq/Charset"> Mutt WikiWiki</uri>.
</p>

</body>
</section>
<section>
<title>Testing it all out</title>
<body>

<p>
There are numerous UTF-8 test websites around.  <c>net-www/w3m</c>,
<c>net-www/links</c>, <c>net-www/elinks</c>, <c>net-www/lynx</c> and all
Mozilla based browsers (including Firefox) support UTF-8. Konqueror and Opera
have full UTF-8 support too.
</p>

<p>
When using one of the text-only web browsers, make absolutely sure you are
using a Unicode-aware terminal.
</p>

<p>
If you see certain characters displayed as boxes with letters or numbers
inside, this means that your font does not have a character for the symbol or
glyph that the UTF-8 wants. Instead, it displays a box with the hex code of the
UTF-8 symbol.
</p>

<ul>
  <li>
    <uri link="http://www.w3.org/2001/06/utf-8-test/UTF-8-demo.html">A W3C
    UTF-8 Test Page</uri>
  </li>
  <li>
    <uri link="http://titus.uni-frankfurt.de/indexe.htm?/unicode/unitest.htm">
    A UTF-8 test page provided by the University of Frankfurt</uri>
  </li>
</ul>

</body>
</section>
<section>
<title>Input Methods</title>
<body>

<p>
<e>Dead keys</e> may be used to input characters in X that are not included on
your keyboard. These work by pressing your right Alt key (or in some countries,
AltGr) and an optional key from the non-alphabetical section of the keyboard to
the left of the return key at once, releasing them, and then pressing a letter.
The dead key should modify it. Input can be further modified by using the Shift
key at the same time as pressing the AltGr and modifier.
</p>

<p>
To enable dead keys in X, you need a layout that supports it. Most European
layouts already have dead keys with the default variant.  However, this is not
true of North American layouts. Although there is a degree of inconsistency
between layouts, the easiest solution seems to be to use a layout in the form
"en_US" rather than "us", for example. The layout is set in
<path>/etc/X11/xorg.conf</path> like so:
</p>

<pre caption="/etc/X11/xorg.conf snippet">
Section "InputDevice"
    Identifier "Keyboard0"
    Driver     "kbd"
    Option     "XkbLayout" "en_US" <comment># Rather than just "us"</comment>
    <comment>(Other Xkb options here)</comment>
EndSection
</pre>

<note>
The preceding change only needs to be applied if you are using a North American
layout, or another layout where dead keys do not seem to be working. European
users should have working dead keys as is.
</note>

<p>
This change will come into effect when your X server is restarted. To apply the
change now, use the <c>setxkbmap</c> tool, for example, <c>setxkbmap en_US</c>.
</p>

<p>
It is probably easiest to describe dead keys with examples. Although the
results are locale dependent, the concepts should remain the same regardless of
locale. The examples contain UTF-8, so to view them you need to either tell
your browser to view the page as UTF-8, or have a UTF-8 locale already
configured.
</p>

<p>
When I press AltGr and [ at once, release them, and then press a, 'ä' is
produced. When I press AltGr and [ at once, and then press e, 'ë' is produced.
When I press AltGr and ; at once, 'á' is produced, and when I press AltGr and ;
at once, release them, and then press e, 'é' is produced.
</p>

<p>
By pressing AltGr, Shift and [ at once, releasing them, and then pressing a, a
Scandinavian 'å' is produced. Similarly, when I press AltGr, Shift and [ at
once, release <e>only</e> the [, and then press it again, '˚' is produced.
Although it looks like one, this (U+02DA) is not the same as a degree symbol
(U+00B0). This works for other accents produced by dead keys — AltGr and [,
releasing only the [, then pressing it again makes '¨'.
</p>

<p>
AltGr can be used with alphabetical keys alone. For example, AltGr and m, a
Greek lower-case letter mu is produced: 'µ'.
</p>

</body>
</section>
<section>
<title>Resources</title>
<body>

<ul>
  <li>
    <uri link="http://www.wikipedia.com/wiki/Unicode">The Wikipedia entry for
    Unicode</uri>
  </li>
  <li>
    <uri link="http://www.wikipedia.com/wiki/UTF-8">The Wikipedia entry for
    UTF-8</uri>
  </li>
  <li><uri link="http://www.unicode.org">Unicode.org</uri></li>
  <li><uri link="http://www.utf-8.com">UTF-8.com</uri></li>
  <li><uri link="http://www.ietf.org/rfc/rfc3629.txt">RFC 3629</uri></li>
  <li><uri link="http://www.ietf.org/rfc/rfc2277.txt">RFC 2277</uri></li>
  <li>
    <uri
    link="http://www.tbray.org/ongoing/When/200x/2003/04/26/UTF">Characters vs.
    Bytes</uri>
  </li>
</ul>

</body>
</section>
</chapter>
</guide>