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1 <?xml version='1.0' encoding="UTF-8"?>
2 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/utf-8.xml,v 1.15 2005/05/29 16:00:59 swift Exp $ -->
3 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
5 <guide link="/doc/en/utf-8.xml">
6 <title>Using UTF-8 with Gentoo</title>
8 <author title="Author">
9 <mail link="slarti@gentoo.org">Thomas Martin</mail>
10 </author>
11 <author title="Contributor">
12 <mail link="devil@gentoo.org.ua">Alexander Simonov</mail>
13 </author>
15 <abstract>
16 This guide shows you how to set up and use the UTF-8 Unicode character set with
17 your Gentoo Linux system, after explaining the benefits of Unicode and more
18 specifically UTF-8.
19 </abstract>
21 <license />
23 <version>2.1</version>
24 <date>2005-06-02</date>
26 <chapter>
27 <title>Character Encodings</title>
28 <section>
29 <title>What is a Character Encoding?</title>
30 <body>
32 <p>
33 Computers do not understand text themselves. Instead, every character is
34 represented by a number. Traditionally, each set of numbers used to represent
35 alphabets and characters (known as a coding system, encoding or character set)
36 was limited in size due to limitations in computer hardware.
37 </p>
39 </body>
40 </section>
41 <section>
42 <title>The History of Character Encodings</title>
43 <body>
45 <p>
46 The most common (or at least the most widely accepted) character set is
47 <b>ASCII</b> (American Standard Code for Information Interchange). It is widely
48 held that ASCII is the most successful software standard ever. Modern ASCII
49 was standardised in 1986 (ANSI X3.4, RFC 20, ISO/IEC 646:1991, ECMA-6) by the
50 American National Standards Institute.
51 </p>
53 <p>
54 ASCII is strictly seven-bit, meaning that it uses bit patterns representable
55 with seven binary digits, which provides a range of 0 to 127 in decimal. These
56 include 32 non-visible control characters, most between 0 and 31, with the
57 final control character, DEL or delete at 127. Characters 32 to 126 are
58 visible characters: a space, punctuation marks, Latin letters and numbers.
59 </p>
61 <p>
62 The eighth bit in ASCII was originally used as a parity bit for error checking.
63 If this is not desired, it is left as 0. This means that, with ASCII, each
64 character is represented by a single byte.
65 </p>
67 <p>
68 Although ASCII was enough for communication in modern English, in other
69 European languages that include accented characters, things were not so easy.
70 The ISO 8859 standards were developed to meet these needs. They were backwards
71 compatible with ASCII, but instead of leaving the eighth bit blank, they used
72 it to allow another 127 characters in each encoding. ISO 8859's limitations
73 soon came to light, and there are currently 15 variants of the ISO 8859
74 standard (8859-1 through to 8859-15). Outside of the ASCII-compatible byte
75 range of these character sets, there is often conflict between the letters
76 represented by each byte. To complicate interoperability between character
77 encodings further, Windows-1252 is used in some versions of Microsoft Windows
78 instead for Western European languages. This is a superset of ISO 8859-1,
79 however it is different in several ways. These sets do all retain ASCII
80 compatibility, however.
81 </p>
83 <p>
84 The necessary development of completely different single-byte encodings for
85 non-Latin alphabets, such as EUC (Extended Unix Coding) which is used for
86 Japanese and Korean (and to a lesser extent Chinese) created more confusion,
87 while other operating systems still used different character sets for the same
88 languages, for example, Shift-JIS and ISO-2022-JP. Users wishing to view
89 cyrillic glyphs had to choose between KOI8-R for Russian and Bulgarian or
90 KOI8-U for Ukrainian, as well as all the other cyrillic encodings such as the
91 unsuccessful ISO 8859-5, and the common Windows-1251 set. All of these
92 character sets broke most compatibility with ASCII (although KOI8 encodings
93 place cyrillic characters in Latin order, so in case the eighth bit is
94 stripped, text is still decipherable on an ASCII terminal through case-reversed
95 transliteration.)
96 </p>
98 <p>
99 This has led to confusion, and also to an almost total inability for
100 multilingual communication, especially across different alphabets. Enter
101 Unicode.
102 </p>
104 </body>
105 </section>
106 <section>
107 <title>What is Unicode?</title>
108 <body>
110 <p>
111 Unicode throws away the traditional single-byte limit of character sets. It
112 uses 17 "planes" of 65,536 code points to describe a maximum of 1,114,112
113 characters. As the first plane, aka. "Basic Multilingual Plane" or BMP,
114 contains almost everything you will ever use, many have made the wrong
115 assumption that Unicode was a 16-bit character set.
116 </p>
118 <p>
119 Unicode has been mapped in many different ways, but the two most common are
120 <b>UTF</b> (Unicode Transformation Format) and <b>UCS</b> (Universal Character
121 Set). A number after UTF indicates the number of bits in one unit, while the
122 number after UCS indicates the number of bytes. UTF-8 has become the most
123 widespread means for the interchange of Unicode text as a result of its
124 eight-bit clean nature, and it is the subject of this document.
125 </p>
127 </body>
128 </section>
129 <section>
130 <title>UTF-8</title>
131 <body>
133 <p>
134 UTF-8 is a variable-length character encoding, which in this instance means
135 that it uses 1 to 4 bytes per symbol. So, the first UTF-8 byte is used for
136 encoding ASCII, giving the character set full backwards compatibility with
137 ASCII. UTF-8 means that ASCII and Latin characters are interchangeable with
138 little increase in the size of the data, because only the first bit is used.
139 Users of Eastern alphabets such as Japanese, who have been assigned a higher
140 byte range are unhappy, as this results in as much as a 50% redundancy in their
141 data.
142 </p>
144 </body>
145 </section>
146 <section>
147 <title>What UTF-8 Can Do for You</title>
148 <body>
150 <p>
151 UTF-8 allows you to work in a standards-compliant and internationally accepted
152 multilingual environment, with a comparatively low data redundancy. UTF-8 is
153 the preferred way for transmitting non-ASCII characters over the Internet,
154 through Email, IRC or almost any other medium. Despite this, many people regard
155 UTF-8 in online communication as abusive. It is always best to be aware of the
156 attitude towards UTF-8 in a specific channel, mailing list or Usenet group
157 before using <e>non-ASCII</e> UTF-8.
158 </p>
160 </body>
161 </section>
162 </chapter>
164 <chapter>
165 <title>Setting up UTF-8 with Gentoo Linux</title>
166 <section>
167 <title>Finding or Creating UTF-8 Locales</title>
168 <body>
170 <p>
171 Now that you understand the principles behind Unicode, you're ready to start
172 using UTF-8 with your system.
173 </p>
175 <p>
176 The preliminary requirement for UTF-8 is to have a version of glibc installed
177 that has national language support. The recommend means to do this is the
178 <path>/etc/locales.build</path> file in combination with the <c>userlocales</c>
179 USE flag. It is beyond the scope of this document to explain the usage of this
180 file though, luckily, the usage of this file is well documented in the comments
181 within it. It is also explained in the <uri
182 link="/doc/en/guide-localization.xml#doc_chap3_sect3"> Gentoo Localisation
183 Guide</uri>.
184 </p>
186 <p>
187 Next, we'll need to decide whether a UTF-8 locale is already available for our
188 language, or whether we need to create one.
189 </p>
191 <pre caption="Checking for an existing UTF-8 locale">
192 <comment>(Replace "en_GB" with your desired locale setting)</comment>
193 # <i>locale -a | grep 'en_GB'</i>
194 en_GB
195 en_GB.UTF-8
196 </pre>
198 <p>
199 From the output of this command line, we need to take the result with a suffix
200 similar to <c>.UTF-8</c>. If there is no result with a suffix similar to
201 <c>.UTF-8</c>, we need to create a UTF-8 compatible locale.
202 </p>
204 <note>
205 Only execute the following code listing if you do not have a UTF-8 locale
206 available for your language.
207 </note>
209 <pre caption="Creating a UTF-8 locale">
210 <comment>(Replace "en_GB" with your desired locale setting)</comment>
211 # <i>localedef -i en_GB -f UTF-8 en_GB.UTF-8</i>
212 </pre>
214 <p>
215 Another way to include a UTF-8 locale is to add it to the
216 <path>/etc/locales.build</path> file and rebuild <c>glibc</c> with the
217 <c>userlocales</c> USE flag set.
218 </p>
220 <pre caption="Line in /etc/locales.build">
221 en_GB.UTF-8/UTF-8
222 </pre>
224 </body>
225 </section>
226 <section>
227 <title>Setting the Locale</title>
228 <body>
230 <p>
231 There is one environment variables that needs to be set in order to use
232 our new UTF-8 locales: <c>LC_ALL</c> (this variable overrides the <c>LANG</c> setting as well). There are also
233 many different ways to set it; some people prefer to only have a UTF-8
234 environment for a specific user, in which case they set them in their
235 <path>~/.profile</path> or <path>~/.bashrc</path>. Others prefer to set the
236 locale globally. One specific circumstance where the author particularly
237 recommends doing this is when <path>/etc/init.d/xdm</path> is in use, because
238 this init script starts the display manager and desktop before any of the
239 aforementioned shell startup files are sourced, and so before any of the
240 variables are in the environment.
241 </p>
243 <p>
244 Setting the locale globally should be done using
245 <path>/etc/env.d/02locale</path>. The file should look something like the
246 following:
247 </p>
249 <pre caption="Demonstration /etc/env.d/02locale">
250 <comment>(As always, change "en_GB.UTF-8" to your locale)</comment>
251 LC_ALL="en_GB.UTF-8"
252 </pre>
254 <p>
255 Next, the environment must be updated with the change.
256 </p>
258 <pre caption="Updating the environment">
259 # <i>env-update</i>
260 >>> Regenerating /etc/ld.so.cache...
261 * Caching service dependencies ...
262 # <i>source /etc/profile</i>
263 </pre>
265 <p>
266 Now, run <c>locale</c> with no arguments to see if we have the correct
267 variables in our environment:
268 </p>
270 <pre caption="Checking if our new locale is in the environment">
271 # <i>locale</i>
272 LANG=
273 LC_CTYPE="en_GB.UTF-8"
274 LC_NUMERIC="en_GB.UTF-8"
275 LC_TIME="en_GB.UTF-8"
276 LC_COLLATE="en_GB.UTF-8"
279 LC_PAPER="en_GB.UTF-8"
280 LC_NAME="en_GB.UTF-8"
281 LC_ADDRESS="en_GB.UTF-8"
285 LC_ALL=en_GB.UTF-8
286 </pre>
288 <p>
289 That's everything. You are now using UTF-8 locales, and the next hurdle is the
290 configuration of the applications you use from day to day.
291 </p>
293 </body>
294 </section>
295 </chapter>
297 <chapter>
298 <title>Application Support</title>
299 <section>
300 <body>
302 <p>
303 When Unicode first started gaining momentum in the software world, multibyte
304 character sets were not well suited to languages like C, in which many of the
305 day-to-day programs people use are written. Even today, some programs are not
306 able to handle UTF-8 properly. Fortunately, most are!
307 </p>
309 </body>
310 </section>
311 <section>
312 <title>Filenames, NTFS, and FAT</title>
313 <body>
315 <p>
316 There are several NLS options in the Linux kernel configuration menu, but it is
317 important to not become confused! For the most part, the only thing you need to
318 do is to build UTF-8 NLS support into your kernel, and change the default NLS
319 option to utf8.
320 </p>
322 <pre caption="Kernel configuration steps for UTF-8 NLS">
323 File Systems --&gt;
324 Native Language Support --&gt;
325 (utf8) Default NLS Option
326 &lt;*&gt; NLS UTF8
327 <comment>(Also &lt;*&gt; other character sets that are in use in
328 your FAT filesystems or Joilet CD-ROMs.)</comment>
329 </pre>
331 <p>
332 If you plan on mounting NTFS partitions, you may need to specify an <c>nls=</c>
333 option with mount. For more information, see <c>man mount</c>.
334 </p>
336 <p>
337 For changing the encoding of filenames, <c>app-text/convmv</c> can be used.
338 </p>
340 <pre caption="Example usage of convmv">
341 # <i>emerge --ask app-text/convmv</i>
342 # <i>convmv -f current-encoding -t utf-8 filename</i>
343 </pre>
345 <p>
346 For changing the <e>contents</e> of files, use the <c>iconv</c> utility,
347 bundled with <c>glibc</c>:
348 </p>
350 <pre caption="Example usage of iconv">
351 <comment>(substitute iso-8859-1 with the charset you are converting from)</comment>
352 <comment>(Check the output is sane)</comment>
353 # <i>iconv -f iso-8859-1 -t utf-8 filename</i>
354 <comment>(Convert a file, you must create another file)</comment>
355 # <i>iconv -f iso-8859-1 -t utf-8 filename > newfile</i>
356 </pre>
358 <p>
359 <c>app-text/recode</c> can also be used for this purpose.
360 </p>
362 </body>
363 </section>
364 <section>
365 <title>The System Console</title>
366 <body>
368 <impo>
369 You need >=sys-apps/baselayout-1.11.9 for Unicode on the console.
370 </impo>
372 <p>
373 To enable UTF-8 on the console, you should edit <path>/etc/rc.conf</path> and
374 set <c>UNICODE="yes"</c>, and also read the comments in that file -- it is
375 important to have a font that has a good range of characters if you plan on
376 making the most of Unicode.
377 </p>
379 <p>
380 The <c>KEYMAP</c> variable, set in <path>/etc/conf.d/keymaps</path>, should
381 have a Unicode keymap specified. To do this, simply prepend the keymap already
382 specified there with -u.
383 </p>
385 <pre caption="Example /etc/conf.d/keymaps snippet">
386 <comment>(Change "uk" to your local layout)</comment>
387 KEYMAP="-u uk"
388 </pre>
390 </body>
391 </section>
392 <section>
393 <title>Ncurses and Slang</title>
394 <body>
396 <note>
397 Ignore any mention of Slang in this section if you do not have it installed or
398 do not use it.
399 </note>
401 <p>
402 It is wise to add <c>unicode</c> to your global USE flags in
403 <path>/etc/make.conf</path>, and then to remerge <c>sys-libs/ncurses</c> and
404 also <c>sys-libs/slang</c> if appropriate:
405 </p>
407 <pre caption="Emerging ncurses and slang">
408 <comment>(We avoid putting these libraries in our world file with --oneshot)</comment>
409 # <i>emerge --oneshot --verbose --ask sys-libs/ncurses sys-libs/slang</i>
410 </pre>
412 <p>
413 We also need to rebuild packages that link to these, now the USE changes have
414 been applied. The tool we use (<c>revdep-rebuild</c>) is part of the
415 <c>gentoolkit</c> package.
416 </p>
418 <pre caption="Rebuilding of programs that link to ncurses or slang">
419 # <i>revdep-rebuild --soname libncurses.so.5</i>
420 # <i>revdep-rebuild --soname libslang.so.1</i>
421 </pre>
423 </body>
424 </section>
425 <section>
426 <title>KDE, GNOME and Xfce</title>
427 <body>
429 <p>
430 All of the major desktop environments have full Unicode support, and will
431 require no further setup than what has already been covered in this guide. This
432 is because the underlying graphical toolkits (Qt or GTK+2) are UTF-8 aware.
433 Subsequently, all applications running on top of these toolkits should be
434 UTF-8-aware out of the box.
435 </p>
437 <p>
438 The exceptions to this rule come in Xlib and GTK+1. GTK+1 requires a
439 iso-10646-1 FontSpec in the ~/.gtkrc, for example
440 <c>-misc-fixed-*-*-*-*-*-*-*-*-*-*-iso10646-1</c>. Also, applications using
441 Xlib or Xaw will need to be given a similar FontSpec, otherwise they will not
442 work.
443 </p>
445 <note>
446 If you have a version of the gnome1 control center around, use that instead.
447 Pick any iso10646-1 font from there.
448 </note>
450 <pre caption="Example ~/.gtkrc (for GTK+1) that defines a Unicode compatible font">
451 style "user-font"
452 {
453 fontset="-misc-fixed-*-*-*-*-*-*-*-*-*-*-iso10646-1"
454 }
455 widget_class "*" style "user-font"
456 </pre>
458 <p>
459 If an application has support for both a Qt and GTK+2 GUI, the GTK+2 GUI will
460 generally give better results with Unicode.
461 </p>
463 </body>
464 </section>
465 <section>
466 <title>X11 and Fonts</title>
467 <body>
469 <impo>
470 <c>x11-base/xorg-x11</c> has far better support for Unicode than XFree86
471 and is <e>highly</e> recommended.
472 </impo>
474 <p>
475 TrueType fonts have support for Unicode, and most of the fonts that ship with
476 Xorg have impressive character support, although, obviously, not every single
477 glyph available in Unicode has been created for that font. To build fonts
478 (including the Bitstream Vera set) with support for East Asian letters with X,
479 make sure you have the <c>cjk</c> USE flag set. Many other applications utilise
480 this flag, so it may be worthwhile to add it as a permanent USE flag.
481 </p>
483 <p>
484 Also, several font packages in Portage are Unicode aware.
485 </p>
487 <pre caption="Optional: Install some more Unicode-aware fonts">
488 # <i>emerge terminus-font intlfonts freefonts cronyx-fonts corefonts</i>
489 </pre>
491 </body>
492 </section>
493 <section>
494 <title>Window Managers and Terminal Emulators</title>
495 <body>
497 <p>
498 Window managers not built on GTK or Qt generally have very good Unicode
499 support, as they often use the Xft library for handling fonts. If your window
500 manager does not use Xft for fonts, you can still use the FontSpec mentioned in
501 the previous section as a Unicode font.
502 </p>
504 <p>
505 Terminal emulators that use Xft and support Unicode are harder to come by.
506 Aside from Konsole and gnome-terminal, the best options in Portage are
507 <c>x11-terms/rxvt-unicode</c>, <c>xfce-extra/terminal</c>,
508 <c>gnustep-apps/terminal</c>, <c>x11-terms/mlterm</c>, <c>x11-terms/mrxvt</c> or
509 plain <c>x11-terms/xterm</c> when built with the <c>unicode</c> USE flag and
510 invoked as <c>uxterm</c>. <c>app-misc/screen</c> supports UTF-8 too, when
511 invoked as <c>screen -u</c> or the following is put into the
512 <path>~/.screenrc</path>:
513 </p>
515 <pre caption="~/.screenrc for UTF-8">
516 defutf8 on
517 </pre>
519 </body>
520 </section>
521 <section>
522 <title>Vim, Emacs, Xemacs and Nano</title>
523 <body>
525 <p>
526 Vim, Emacs and Xemacs provide full UTF-8 support, and also have builtin
527 detection of UTF-8 files. For further information in Vim, use <c>:help
528 mbyte.txt</c>.
529 </p>
531 <p>
532 Nano currently does not provide support for UTF-8, although it has been planned
533 for a long time. With luck, this will change in future. At the time of writing,
534 UTF-8 support is in Nano's CVS, and should be included in the next release.
535 </p>
537 </body>
538 </section>
539 <section>
540 <title>Shells</title>
541 <body>
543 <p>
544 Currently, <c>bash</c> provides full Unicode support through the GNU readline
545 library. Z Shell users are in a somewhat worse position -- no parts of the
546 shell have Unicode support, although there is a concerted effort to add
547 multibyte character set support underway at the moment.
548 </p>
550 <p>
551 The C shell, <c>tcsh</c> and <c>ksh</c> do not provide UTF-8 support at all.
552 </p>
554 </body>
555 </section>
556 <section>
557 <title>Irssi</title>
558 <body>
560 <p>
561 Since 0.8.10, Irssi has complete UTF-8 support, although it does require a user
562 to set an option.
563 </p>
565 <pre caption="Enabling UTF-8 in Irssi">
566 /set term_charset UTF-8
567 </pre>
569 <p>
570 For channels where non-ASCII characters are often exchanged in non-UTF-8
571 charsets, the <c>/recode</c> command may be used to convert the characters.
572 Type <c>/help recode</c> for more information.
573 </p>
575 </body>
576 </section>
577 <section>
578 <title>Mutt</title>
579 <body>
581 <p>
582 The Mutt mail user agent has very good Unicode support. To use UTF-8 with Mutt,
583 put the following in your <path>~/.muttrc</path>:
584 </p>
586 <pre caption="~/.muttrc for UTF-8">
587 set send_charset="utf8" <comment>(outgoing character set)</comment>
588 set charset="utf8" <comment>(display character set)</comment>
589 </pre>
591 <note>
592 You may still see '?' in mail you read with Mutt. This is a result of people
593 using a mail client which does not indicate the used charset. You can't do much
594 about this than to ask them to configure their client correctly.
595 </note>
597 <p>
598 Further information is available from the <uri
599 link="http://wiki.mutt.org/index.cgi?MuttFaq/Charset"> Mutt WikiWiki</uri>.
600 </p>
602 </body>
603 </section>
604 <section>
605 <title>Less</title>
606 <body>
608 <p>
609 We all use a lot of <c>more</c> or <c>less</c> along with the <c>|</c> to be
610 able to correctly see the output of a command, like for example
611 <c>dmesg | less</c>. While <c>more</c> only needs the shell to be UTF-8 aware,
612 <c>less</c> needs an environment variable set, <c>LESSCHARSET</c> to ensure
613 that unicode characters are rendered correctly. This can be set in
614 <path>/etc/profile</path> or <path>~/.bash_profile</path>. Fire up the editor
615 of your choice and the add the following line to one of the files mentioned
616 above.
617 </p>
619 <pre caption="Setting up the Environment variable for less">
621 </pre>
623 </body>
624 </section>
625 <section>
626 <title>Man</title>
627 <body>
629 <p>
630 Man pages are an integral part of any Linux machine. To ensure that any
631 unicode in your man pages render correctly, edit <path>/etc/man.conf</path>
632 and replace a line as shown below.
633 </p>
635 <pre caption="man.conf changes for Unicode support">
636 <comment>(This is the old line)</comment>
637 NROFF /usr/bin/nroff -Tascii -c -mandoc
638 <comment>(Replace the one above with this)</comment>
639 NROFF /usr/bin/nroff -mandoc -c
640 </pre>
642 </body>
643 </section>
644 <section>
645 <title>Testing it all out</title>
646 <body>
648 <p>
649 There are numerous UTF-8 test websites around. <c>net-www/w3m</c>,
650 <c>net-www/links</c>, <c>net-www/elinks</c>, <c>net-www/lynx</c> and all
651 Mozilla based browsers (including Firefox) support UTF-8. Konqueror and Opera
652 have full UTF-8 support too.
653 </p>
655 <p>
656 When using one of the text-only web browsers, make absolutely sure you are
657 using a Unicode-aware terminal.
658 </p>
660 <p>
661 If you see certain characters displayed as boxes with letters or numbers
662 inside, this means that your font does not have a character for the symbol or
663 glyph that the UTF-8 wants. Instead, it displays a box with the hex code of the
664 UTF-8 symbol.
665 </p>
667 <ul>
668 <li>
669 <uri link="http://www.w3.org/2001/06/utf-8-test/UTF-8-demo.html">A W3C
670 UTF-8 Test Page</uri>
671 </li>
672 <li>
673 <uri link="http://titus.uni-frankfurt.de/indexe.htm?/unicode/unitest.htm">
674 A UTF-8 test page provided by the University of Frankfurt</uri>
675 </li>
676 </ul>
678 </body>
679 </section>
680 <section>
681 <title>Input Methods</title>
682 <body>
684 <p>
685 <e>Dead keys</e> may be used to input characters in X that are not included on
686 your keyboard. These work by pressing your right Alt key (or in some countries,
687 AltGr) and an optional key from the non-alphabetical section of the keyboard to
688 the left of the return key at once, releasing them, and then pressing a letter.
689 The dead key should modify it. Input can be further modified by using the Shift
690 key at the same time as pressing the AltGr and modifier.
691 </p>
693 <p>
694 To enable dead keys in X, you need a layout that supports it. Most European
695 layouts already have dead keys with the default variant. However, this is not
696 true of North American layouts. Although there is a degree of inconsistency
697 between layouts, the easiest solution seems to be to use a layout in the form
698 "en_US" rather than "us", for example. The layout is set in
699 <path>/etc/X11/xorg.conf</path> like so:
700 </p>
702 <pre caption="/etc/X11/xorg.conf snippet">
703 Section "InputDevice"
704 Identifier "Keyboard0"
705 Driver "kbd"
706 Option "XkbLayout" "en_US" <comment># Rather than just "us"</comment>
707 <comment>(Other Xkb options here)</comment>
708 EndSection
709 </pre>
711 <note>
712 The preceding change only needs to be applied if you are using a North American
713 layout, or another layout where dead keys do not seem to be working. European
714 users should have working dead keys as is.
715 </note>
717 <p>
718 This change will come into effect when your X server is restarted. To apply the
719 change now, use the <c>setxkbmap</c> tool, for example, <c>setxkbmap en_US</c>.
720 </p>
722 <p>
723 It is probably easiest to describe dead keys with examples. Although the
724 results are locale dependent, the concepts should remain the same regardless of
725 locale. The examples contain UTF-8, so to view them you need to either tell
726 your browser to view the page as UTF-8, or have a UTF-8 locale already
727 configured.
728 </p>
730 <p>
731 When I press AltGr and [ at once, release them, and then press a, 'ä' is
732 produced. When I press AltGr and [ at once, and then press e, 'ë' is produced.
733 When I press AltGr and ; at once, 'á' is produced, and when I press AltGr and ;
734 at once, release them, and then press e, 'é' is produced.
735 </p>
737 <p>
738 By pressing AltGr, Shift and [ at once, releasing them, and then pressing a, a
739 Scandinavian 'å' is produced. Similarly, when I press AltGr, Shift and [ at
740 once, release <e>only</e> the [, and then press it again, '˚' is produced.
741 Although it looks like one, this (U+02DA) is not the same as a degree symbol
742 (U+00B0). This works for other accents produced by dead keys — AltGr and [,
743 releasing only the [, then pressing it again makes '¨'.
744 </p>
746 <p>
747 AltGr can be used with alphabetical keys alone. For example, AltGr and m, a
748 Greek lower-case letter mu is produced: 'µ'. AltGr and s produce a
749 scharfes s or esszet: 'ß'. As many European users would expect (because
750 it is marked on their keyboard), AltGr and 4 produces a Euro sign, '€'.
751 </p>
753 </body>
754 </section>
755 <section>
756 <title>Resources</title>
757 <body>
759 <ul>
760 <li>
761 <uri link="http://www.wikipedia.com/wiki/Unicode">The Wikipedia entry for
762 Unicode</uri>
763 </li>
764 <li>
765 <uri link="http://www.wikipedia.com/wiki/UTF-8">The Wikipedia entry for
766 UTF-8</uri>
767 </li>
768 <li><uri link="http://www.unicode.org">Unicode.org</uri></li>
769 <li><uri link="http://www.utf-8.com">UTF-8.com</uri></li>
770 <li><uri link="http://www.ietf.org/rfc/rfc3629.txt">RFC 3629</uri></li>
771 <li><uri link="http://www.ietf.org/rfc/rfc2277.txt">RFC 2277</uri></li>
772 <li>
773 <uri
774 link="http://www.tbray.org/ongoing/When/200x/2003/04/26/UTF">Characters vs.
775 Bytes</uri>
776 </li>
777 </ul>
779 </body>
780 </section>
781 </chapter>
782 </guide>

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