The Unicode HOWTO
Bruno Haible,<haible@clisp.cons.org>
v0.12, 19 October 1999
This document describes how to change your Linux system so it uses
UTF-8 as text encoding. - This is work in progress. Any tips, patches,
pointers, URLs are very welcome.
______________________________________________________________________
Table of Contents
1. Introduction
1.1 Why Unicode?
1.2 Unicode encodings
1.2.1 Footnotes for C/C++ developers
1.3 Related resources
2. Display setup
2.1 Linux console
2.2 X11 Foreign fonts
2.3 X11 Unicode fonts
2.4 Unicode xterm
2.5 Miscellaneous
3. Locale setup
3.1 Files & the kernel
3.2 Ttys & the kernel
3.3 General data conversion
3.4 Locale environment variables
3.5 Creating the locale support files
3.6 Adding support to the C library
3.7 Converting the message catalogs
4. Specific applications
4.1 Networking
4.1.1 rlogin
4.1.2 telnet
4.2 Browsers
4.2.1 Netscape
4.2.2 lynx
4.2.3 Test pages
4.3 Editors
4.3.1 yudit
4.3.2 mined98
4.3.3 vim
4.3.4 emacs
4.3.5 xemacs
4.3.6 nedit
4.3.7 xedit
4.3.8 axe
4.3.9 pico
4.3.10 TeX
4.4 Mailers
4.4.1 pine
4.4.2 kmail
4.4.3 Netscape Communicator
4.4.4 emacs (rmail, vm)
4.5 Other text-mode applications
4.5.1 less
4.5.2 expand, wc
4.5.3 col, colcrt, colrm, column, rev, ul
4.5.4 figlet
4.5.5 kermit
4.6 Other X11 applications
5. Making your programs Unicode aware
5.1 C/C++
5.1.1 For normal text handling
5.1.1.1 Portability notes
5.1.1.2 The libutf8 library
5.1.1.3 The Plan9 way
5.1.2 For graphical user interface
5.1.3 For advanced text handling
5.1.4 For conversion
5.1.5 Other approaches
5.2 Java
5.3 Lisp
5.4 Ada95
______________________________________________________________________
1. Introduction
1.1. Why Unicode?
People in different countries use different characters to represent
the words of their native languages. Nowadays most applications,
including email systems and web browsers, are 8-bit clean, i.e. they
can operate on and display text correctly provided that it is
represented in an 8-bit character set, like ISO-8859-1.
There are far more than 256 characters in the world - think of
cyrillic, hebrew, arabic, chinese, japanese, korean and thai -, and
new characters are being invented now and then. The problems that come
up for users are:
o It is impossible to store text with characters from different
character sets in the same document. For example, I can cite
russian papers in a German or French publication if I use TeX, xdvi
and PostScript, but I cannot do it in plain text.
o As long as every document has its own character set, and
recognition of the character set is not automatic, manual user
intervention is inevitable. For example, in order to view the
homepage of the XTeamLinux distribution
http://www.xteamlinux.com.cn/ I have to tell Netscape that the web
page is coded in GB2312.
o New symbols like the Euro are being invented. ISO has issued a new
standard ISO-8859-15, which is mostly like ISO-8859-1 except that
it removes some rarely used characters (the old currency sign) and
replaced it with the Euro sign. If users adopt this standard, they
have documents in different character sets on their disk, and they
start having to think about it daily. But computers should make
things simpler, not more complicated.
The solution of this problem is the adoption of a world-wide usable
character set. This character set is Unicode http://www.unicode.org/.
For more info about Unicode, do `man 7 unicode' (manpage contained in
the ldpman-1.20 package).
1.2. Unicode encodings
This reduces the user's problem of dealing with character sets to a
technical problem: How to transport Unicode characters using the 8-bit
bytes? 8-bit units are the smallest addressing units of most
computers and also the unit used by TCP/IP network connections. The
use of 1 byte to represent 1 character is, however, an accident of
history, caused by the fact that computer development started in
Europe and the U.S. where 96 characters were found to be sufficient
for a long time.
There are basically four ways to encode Unicode characters in bytes:
UTF-8
128 characters are encoded using 1 byte (the ASCII characters).
1920 characters are encoded using 2 bytes (Roman, Greek,
Cyrillic, Coptic, Armenian, Hebrew, Arabic characters). 63488
characters are encoded using 3 bytes (Chinese and Japanese among
others). The other 2147418112 characters (not assigned yet) can
be encoded using 4, 5 or 6 characters. For more info about
UTF-8, do `man 7 utf-8' (manpage contained in the ldpman-1.20
package).
UCS-2
Every character is represented as two bytes. This encoding can
only represent the first 65536 Unicode characters.
UTF-16
This is an extension of UCS-2 which can represent 1114112
Unicode characters. The first 65536 Unicode characters are
represented as two bytes, the other ones as four bytes.
UCS-4
Every character is represented as four bytes.
The space requirements for encoding a text, compared to encodings
currently in use (8 bit per character for European languages, more for
Chinese/Japanese/Korean), is as follows. This has an influence on disk
storage space and network download speed.
UTF-8
No change for US ASCII, just a few percent more for ISO-8859-1,
50% more for Chinese/Japanese/Korean, 100% more for Greek and
Cyrillic.
UCS-2 and UTF-16
No change for Chinese/Japanese/Korean. 100% more for US ASCII
and ISO-8859-1, Greek and Cyrillic.
UCS-4
100% more for Chinese/Japanese/Korean. 300% more for US ASCII
and ISO-8859-1, Greek and Cyrillic.
Given the penalty for US and European documents caused by UCS-2,
UTF-16, and UCS-4, it seems unlikely that these encodings have a
potential for wide-scale use. The Microsoft Win32 API supports the
UCS-2 encoding since 1995 (at least), yet this encoding has not been
widely adopted for documents - SJIS remains prevalent in Japan.
UTF-8 on the other hand has the potential for wide-scale use, since it
doesn't penalize US and European users, and since many text processing
programs don't need to be changed for UTF-8 support.
In the following, we will describe how to change your Linux system so
it uses UTF-8 as text encoding.
1.2.1. Footnotes for C/C++ developers
The Microsoft Win32 approach makes it easy for developers to produce
Unicode versions of their programs: You "#define UNICODE" at the top
of your program and then change many occurrences of `char' to `TCHAR',
until your program compiles without warnings. The problem with it is
that you end up with two versions of your program: one which
understands UCS-2 text but no 8-bit encodings, and one which
understands only old 8-bit encodings.
Moreover, there is an endianness issue with UCS-2 and UCS-4. The IANA
character set registry says about ISO-10646-UCS-2: "this needs to
specify network byte order: the standard does not specify". Network
byte order is big endian. Whereas Microsoft, in its C/C++ development
tools, recommends to use machine-dependent endianness (i.e. little
endian on ix86 processors) and either a byte-order mark at the
beginning of the document, or some statistical heuristics(!).
The UTF-8 approach on the other hand keeps `char*' as the standard C
string type. As a result, your program will handle US ASCII text,
independently of any environment variables, and will handle both
ISO-8859-1 and UTF-8 encoded text provided the LANG environment
variable is set accordingly.
1.3. Related resources
Markus Kuhn's very up-to-date resource list:
o http://www.cl.cam.ac.uk/~mgk25/unicode.html
o http://www.cl.cam.ac.uk/~mgk25/ucs-fonts.html
Roman Czyborra's overview of Unicode, UTF-8 and UTF-8 aware programs:
http://czyborra.com/utf/#UTF-8
Some example UTF-8 files:
o The files quickbrown.txt, utf-8-test.txt, utf-8-demo.txt in the
examples directory of Markus Kuhn's ucs-fonts package
http://www.cl.cam.ac.uk/~mgk25/download/ucs-fonts.tar.gz
o ftp://ftp.cs.su.oz.au/gary/x-utf8.html
o The file iso10646 in the Kosta Kostis' trans-1.1.1 package
ftp://ftp.nid.ru/pub/os/unix/misc/trans111.tar.gz
o ftp://ftp.dante.de/pub/tex/info/lwc/apc/utf8.html
o http://www.cogsci.ed.ac.uk/~richard/unicode-sample.html
2. Display setup
We assume you have already adapted your Linux console and X11
configuration to your keyboard and locale. This is explained in the
Danish/International HOWTO, and in the other national HOWTOs: Finnish,
French, German, Italian, Polish, Slovenian, Spanish, Cyrillic, Hebrew,
Chinese, Thai, Esperanto. But please do not follow the advice given in
the Thai HOWTO, to pretend you were using ISO-8859-1 characters
(U0000..U00FF) when what you are typing are actually Thai characters
(U0E01..U0E5B). Doing so will only cause problems when you switch to
Unicode.
2.1. Linux console
I'm not talking much about the Linux console here, because on those
machines on which I don't have xdm running, I use it only to type my
login name, my password, and "xinit".
Anyway, the kbd-0.99 package
ftp://sunsite.unc.edu/pub/Linux/system/keyboards/kbd-0.99.tar.gz and a
heavily extended version, the console-tools-0.2.2 package
ftp://sunsite.unc.edu/pub/Linux/system/keyboards/console-
tools-0.2.2.tar.gz contains in the kbd-0.99/src/ (or console-
tools-0.2.2/screenfonttools/) directory two programs: `unicode_start'
and `unicode_stop'. When you call `unicode_start', the console's
screen output is interpreted as UTF-8. Also, the keyboard is put into
Unicode mode (see "man kbd_mode"). In this mode, Unicode characters
typed as Alt-x1 ... Alt-xn (where x1,...,xn are digits on the numeric
keypad) will be emitted in UTF-8. If your keyboard or, more precisely,
your normal keymap has non-ASCII letter keys (like the German Umlaute)
which you would like to be CapsLockable, you need to apply the kernel
patch linux-2.2.9-keyboard.diff or linux-2.3.12-keyboard.diff.
You will want to use display characters from different scripts on the
same screen. For this, you need a Unicode console font. The
ftp://sunsite.unc.edu/pub/Linux/system/keyboards/console-
data-1999.08.29.tar.gz package contains a font
(LatArCyrHeb-{08,14,16,19}.psf) which covers Latin, Cyrillic, Hebrew,
Arabic scripts. It covers ISO 8859 parts 1,2,3,4,5,6,8,9,10 all at
once. To install it, copy it to /usr/lib/kbd/consolefonts/ and execute
"/usr/bin/setfont /usr/lib/kbd/consolefonts/LatArCyrHeb-14.psf".
If you want cut&paste to work with UTF-8 consoles, you need the patch
linux-2.3.12-console.diff from Edmund Thomas Grimley Evans and
Stanislav Voronyi.
2.2. X11 Foreign fonts
Don't hesitate to install Cyrillic, Chinese, Japanese etc. fonts. Even
if they are not Unicode fonts, they will help in displaying Unicode
documents: at least Netscape Communicator 4 and Java will make use of
foreign fonts when available.
The following programs are useful when installing fonts:
o "mkfontdir directory" prepares a font directory for use by the X
server, needs to be executed after installing fonts in a directory.
o "xset fp+ directory" adds a directory to the X server's current
font path. To add a directory permanently, add a "FontPath" line
to your /etc/XF86Config file, in section "Files".
o "xset fp rehash" needs to be executed after calling mkfontdir on a
directory that is already contained in the X server's current font
path.
o "xfontsel" allows you to browse the installed fonts by selecting
various font properties.
o "xlsfonts -fn fontpattern" lists all fonts matching a font pattern.
Also displays various font properties. In particular, "xlsfonts -ll
-fn font" lists the font properties CHARSET_REGISTRY and
CHARSET_ENCODING, which together determine the font's encoding.
o "xfd -fn font" displays a font page by page.
The following fonts are freely available (not a complete list):
o The ones contained in XFree86, sometimes packaged in separate
packages. For example, SuSE has only normal 75dpi fonts in the
base `xf86' package. The other fonts are in the packages
`xfnt100', `xfntbig', `xfntcyr', `xfntscl'.
o The Emacs international fonts,
ftp://ftp.gnu.org/pub/gnu/intlfonts/intlfonts-1.1.tar.gz As already
mentioned, they are useful even if you prefer XEmacs to GNU Emacs
or don't use any Emacs at all.
2.3. X11 Unicode fonts
Application wishing to display text belonging to different scripts
(like Cyrillic and Greek) at the same time, can do so by using
different X fonts for the various pieces of text. This is what
Netscape Communicator and Java do. However, this approach is more
complicated, because instead of working with `Font' and `XFontStruct',
the programmer has to deal with `XFontSet', and also because not all
fonts in the font set need to have the same dimensions.
o Markus Kuhn has assembled fixed-width 75dpi fonts with Unicode
encoding covering Latin, Greek, Cyrillic, Armenian, Georgian,
Hebrew, Symbol scripts. They cover ISO 8859 parts
1,2,3,4,5,7,8,9,10,13,14,15 all at once. This font is required for
running xterm in utf-8 mode.
http://www.cl.cam.ac.uk/~mgk25/download/ucs-fonts.tar.gz
o Roman Czyborra has assembled an 8x16 / 16x16 75dpi font with
Unicode encoding covering a huge part of Unicode. Download
unifont.hex.gz and hex2bdf from http://czyborra.com/unifont/. It
is not fixed-width: 8 pixels wide for European characters, 16
pixels wide for Chinese characters. Installation instructions:
$ gunzip unifont.hex.gz
$ hex2bdf < unifont.hex > unifont.bdf
$ bdftopcf -o unifont.pcf unifont.bdf
$ gzip -9 unifont.pcf
# cp unifont.pcf.gz /usr/X11R6/lib/X11/fonts/misc
# cd /usr/X11R6/lib/X11/fonts/misc
# mkfontdir
# xset fp rehash
o Primoz Peterlin has assembled an ETL family fonts covering Latin,
Greek, Cyrillic, Armenian, Georgian, Hebrew scripts.
ftp://ftp.x.org/contrib/fonts/etl-unicode.tar.gz Use the "bdftopcf"
program in order to install it.
2.4. Unicode xterm
xterm is part of X11R6 and XFree86, but is maintained separately by
Tom Dickey. http://www.clark.net/pub/dickey/xterm/xterm.html Newer
versions (patch level 109 and above) contain support for converting
keystrokes to UTF-8 before sending them to the application running in
the xterm, and for displaying Unicode characters that the application
outputs as UTF-8 byte sequence.
To get an UTF-8 xterm running, you need to:
o Fetch http://www.clark.net/pub/dickey/xterm/xterm.tar.gz,
o Configure it by calling "./configure --enable-wide-chars ...", then
compile and install it.
o Have a Unicode fixed-width font installed. Markus Kuhn's ucs-
fonts.tar.gz (see above) is made for this.
o Start "xterm -u8 -fn fixed". The option "-u8" turns on Unicode and
UTF-8 handling. The "fixed" font is Markus Kuhn's Unicode font.
o Take a look at the sample files contained in Markus Kuhn's ucs-
fonts package:
$ cd .../ucs-fonts
$ cat quickbrown.txt
$ cat utf-8-demo.txt
You should be seeing (among others) greek and russian characters.
o To make xterm come up with UTF-8 handling each time it is started,
add the line XTerm*utf8: 1 to your $HOME/.Xdefaults (for yourself
only). I don't recommend changing the system-wide
/usr/X11R6/lib/X11/app-defaults/XTerm, because then your changes
will be erased next time you upgrade to a new XFree86 version.
o If you also changed the font name, you need a line of the form
*VT100*font: your-font in your $HOME/.Xdefaults. For "fixed" it is
not needed, because "fixed" is the default anyway.
2.5. Miscellaneous
A small program which tests whether a Linux console or xterm is in
UTF-8 mode can be found in the
ftp://sunsite.unc.edu/pub/Linux/system/keyboards/x-lt-1.18.tar.gz
package by Ricardas Cepas, files testUTF-8.c and testUTF8.c.
3. Locale setup
3.1. Files & the kernel
You can now already use any Unicode characters in file names. No
kernel or file utilities need modifications. This is because file
names in the kernel can be anything not containing a null byte, and
'/' is used to delimit subdirectories. When encoded using UTF-8, non-
ASCII characters will never be encoded using null bytes or slashes.
All that happens is that file and directory names occupy more bytes
than they contain characters. For example, a filename consisting of
five greek characters will appear to the kernel as a 10-byte filename.
The kernel does not know (and does not need to know) that these bytes
are displayed as greek.
This is the general theory, as long as your files stay inside Linux.
On filesystems which are used from other operating systems, you have
mount options to control conversion of filenames to/from UTF-8:
o The "vfat" filesystems has a mount option "utf8". See
file:/usr/src/linux/Documentation/filesystems/vfat.txt. When you
give an "iocharset" mount option different from the default (which
is "iso8859-1"), the results with and without "utf8" are not
consistent. Therefore I don't recommend the "iocharset" mount
option.
o The "msdos", "umsdos" filesystems have the same mount option, but
it appears to have no effect.
o The "iso9660" filesystem has a mount option "utf8". See
file:/usr/src/linux/Documentation/filesystems/isofs.txt.
o Since Linux 2.2.x kernels, the "ntfs" filesystem has a mount option
"utf8". See file:/usr/src/linux/Documentation/filesystems/ntfs.txt.
The other filesystems (nfs, smbfs, ncpfs, hpfs, etc.) don't convert
filenames; therefore they support Unicode file names in UTF-8
encoding only if the other operating system supports them. Recall
that to enable a mount option for all future remount, you add to
the fourth column of the corresponding /etc/fstab line.
3.2. Ttys & the kernel
Ttys are some kind of bidirectional pipes between two program,
allowing fancy features like echoing or command-line editing. When in
an xterm, you execute the "cat" command without arguments, you can
enter and edit any number of lines, and they will be echoed back line
by line. The kernel's editing actions are not correct, especially the
Backspace (erase) key and the tab bey are not treated correctly.
To fix this, you need to:
o apply the kernel patch linux-2.0.35-tty.diff or
linux-2.2.9-tty.diff or linux-2.3.12-tty.diff and recompile your
kernel,
o if you are using glibc2, apply the patch glibc211-tty.diff and
recompile your libc (or if you are not so adventurous, it is
sufficient to patch an already installed include file: glibc-
tty.diff),
o apply the patch stty.diff to GNU sh-utils-1.16b, and rebuild the
"stty" program, then test it using "stty -a" and "stty iutf8".
o add the command "stty iutf8" to the "unicode_start" script, and add
the command "stty -iutf8" to the "unicode_stop script.
o apply the patch xterm.diff to xterm-109, and rebuild "xterm", then
test it by starting "xterm -u8"/"xterm +u8" and running "stty -a"
and interactive "cat" inside it.
To make this fix persistent across rlogin and telnet, you also need
to:
o Define new values for the TERM environment variable, "linux-utf8"
as an alias to "linux", and "xterm-utf8" as an alias to "xterm".
If your system has the ncurses library and the /usr/lib/terminfo
(or /usr/share/terminfo) database, do this by running
$ tic linux-utf8.terminfo
$ tic xterm-utf8.terminfo
as non-root (this will create the terminfo entries in your $HOME/.ter-
minfo directory). Here are linux-utf8.terminfo and xterm-utf8.ter-
minfo. I don't recommend running this as root, because it will create
the terminfo entries in /usr/lib/terminfo where they might be erased
next time you upgrade your system. If your system has an /etc/termcap
file, you should also edit that file: copy the linux and xterm entries
and give them the new names "linux-utf8" and "xterm-utf8". For an
example, see termcap.diff.
o Each time you call "unicode_start" or "unicode_stop" from the
console, also execute "export TERM=linux-utf8" or "export
TERM=linux", respectively.
o Apply the patch xterm2.diff to xterm-109, rebuild "xterm", and
remove any "XTerm*termName" line from /usr/X11R6/lib/X11/app-
defaults/XTerm and $HOME/.Xdefaults. Now xterm sets the TERM
variable to "xterm-utf8" instead of "xterm" when running in UTF-8
mode.
o Apply the patches netkit.diff, netkitb.diff and telnet.diff and
rebuild "rlogind" and "telnetd". Now rlogin and telnet put the tty
into UTF-8 editing mode whenever the TERM environment variable is
"linux-utf8" or "xterm-utf8".
3.3. General data conversion
You will need a program to convert your locally (probably ISO-8859-1)
encoded texts to UTF-8. (The alternative would be to keep using texts
in different encodings on the same machine; this is not fun in the
long run.) One such program is `iconv', which comes with glibc-2.1.
Simply use
$ iconv --from-code=ISO-8859-1 --to-code=UTF-8 < old_file > new_file
Here are two handy shell scripts, called "i2u" i2u.sh (for ISO to UTF
conversion) and "u2i" u2i.sh (for UTF to ISO conversion). Adapt
according to your current 8-bit character set.
If you don't have glibc-2.1 and iconv installed, you can use GNU
recode 3.5 instead. "i2u" i2u_recode.sh is "recode
ISO-8859-1..UTF-8", and "u2i" u2i_recode.sh is "recode
UTF-8..ISO-8859-1".
ftp://ftp.iro.umontreal.ca/pub/recode/recode-3.5.tar.gz
ftp://ftp.gnu.org/pub/gnu/recode/recode-3.5.tar.gz Notes: You need GNU
recode 3.5 or newer. To compile GNU recode 3.5 on platforms without
glibc2 (i.e. on all platforms except recent Linux systems), you need
to configure it with --disable-nls, otherwise it won't link.
Or you can also use CLISP instead. Here are "i2u" i2u.lsp and "u2i"
u2i.lsp written in Lisp. Note: You need a CLISP version from July 1999
or newer. ftp://clisp.cons.org/pub/lisp/clisp/source/clispsrc.tar.gz.
Other data conversion programs, less powerful than GNU recode, are
`trans' ftp://ftp.informatik.uni-
erlangen.de/pub/doc/ISO/charsets/trans113.tar.gz, `tcs' from the Plan9
operating system ftp://ftp.informatik.uni-
erlangen.de/pub/doc/ISO/charsets/tcs.tar.gz, and
`utrans'/`uhtrans'/`hutrans'
ftp://ftp.cdrom.com/pub/FreeBSD/distfiles/i18ntools-1.0.tar.gz by G.
Adam Stanislav <adam@whizkidtech.net>.
3.4. Locale environment variables
You may have the following environment variables set, containing
locale names:
LANGUAGE
override for LC_MESSAGES, used by GNU gettext only
LC_ALL
override for all other LC_* variables
LC_CTYPE, LC_MESSAGES, LC_COLLATE, LC_NUMERIC, LC_MONETARY, LC_TIME
individual variables for: character types and encoding, natural
language messages, sorting rules, number formatting, money
amount formatting, date and time display
LANG
default value for all LC_* variables
(See `man 7 locale' for a detailed description.)
Each of the LC_* and LANG variables can contain a locale name of the
following form:
language[_territory[.codeset]][@modifier]
where language is an ISO 639 language code (lower case), territory is
an ISO 3166 country code (upper case), codeset denotes a character
set, and modifier stands for other particular attributes (for example
indicating a particular language dialect, or a nonstandard
orthography).
LANGUAGE can contain several locale names, separated by colons.
In order to tell your system and all applications that you are using
UTF-8, you need to add a codeset suffix of UTF-8 to your locale names.
For example, if you were using
LANGUAGE=de:fr:en
LC_CTYPE=de_DE
you would change this to
LANGUAGE=de.UTF-8:fr.UTF-8:en.UTF-8
LC_CTYPE=de_DE.UTF-8
3.5. Creating the locale support files
If you have glibc-2.1 or glibc-2.1.1 or glibc-2.1.2 installed, first
check using "localedef --help" that the system directory for character
maps is /usr/share/i18n/charmaps. Then apply to the file
/usr/share/i18n/charmaps/UTF8 the patch glibc21.diff or glibc211.diff
or glibc212.diff, respectively. Then create the support files for
each UTF-8 locale you intend to use, for example:
$ localedef -v -c -i de_DE -f UTF8 /usr/share/locale/de_DE.UTF-8
You typically don't need to create locales named "de" or "fr" without
country suffix, because these locales are normally only used by the
LANGUAGE variable and not by the LC_* variables, and LANGUAGE is only
used as an override for LC_MESSAGES.
3.6. Adding support to the C library
The glibc-2.2 will support multibyte locales, in particular the UTF-8
locales created above. But glibc-2.1 or glibc-2.1.1 do not really
support it. Therefore the only real effect of the above creation of
the /usr/share/locale/de_DE.UTF-8/* files is that
`setlocale(LC_ALL,"")' will return "de_DE.UTF-8", according to your
environment variables, instead of stripping off the ".UTF-8" suffix.
To add support for the UTF-8 locale, you should build and install the
`libutf8_plug.so' library, from libutf8-0.5.2.tar.gz. Then you can
set the LD_PRELOAD environment variable to point to the installed
library:
$ export LD_PRELOAD=/usr/local/lib/libutf8_plug.so
Then, in every program launched with this environment variable set,
the functions in libutf8_plug.so will override the original ones in
/lib/libc.so.6. For more info about LD_PRELOAD, see "man 8 ld.so".
This entire thing will not be necessary any more once glibc-2.2 comes
out.
3.7. Converting the message catalogs
Now let's fill these new locales with content. The following /bin/sh
commands can convert your message catalogs to UTF-8 format. They must
be run as root, and require the programs `msgfmt' and `msgunfmt' from
GNU gettext-0.10.35 to be installed. convert-msgcat.sh
This too will not be necessary any more once glibc-2.2 comes out,
because by then, the gettext function will convert the strings
appropriately from the translator's character set to the user's
character set, using either iconv or librecode.
4. Specific applications
4.1. Networking
4.1.1. rlogin
is fine with the above mentioned patches.
4.1.2. telnet
telnet is not 8-bit clean by default. In order to be able to send
Unicode keystrokes to the remote host, you need to set telnet into
"outbinary" mode. There are two ways to do this:
$ telnet -L <host>
and
$ telnet
telnet> set outbinary
telnet> open <host>
Additionally, use the above mentioned patches.
4.2. Browsers
4.2.1. Netscape
Netscape 4.05 or newer can display HTML documents in UTF-8 encoding.
All a document needs is the following line between the <head> and
</head> tags:
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Netscape 4.05 or newer can also display HTML and text files in UCS-2
encoding with byte-order mark.
http://www.netscape.com/computing/download/
4.2.2. lynx
lynx-2.8 has an options screen (key 'O') which permits to set the
display character set. When running in an xterm or Linux console in
UTF-8 mode, set this to "UNICODE UTF-8".
Now, again, all a document needs is the following line between the
<head> and </head> tags:
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
When you are viewing text files in UTF-8 encoding, you also need to
pass the command-line option "-assume_local_charset=UTF-8" (affects
only file:/... URLs) or "-assume_charset=UTF-8" (affects all URLs).
In lynx-2.8.2 you can alternatively, in the options screen (key 'O'),
change the assumed document character set to "utf-8".
There is also an option in the options screen, to set the "preferred
document character set". But it has no effect, at least with file:/...
URLs and with http://... URLs served by apache-1.3.0.
There is a spacing and line-breaking problem, however. (Look at the
russian section of x-utf8.html, or at utf-8-demo.txt.)
Also, in lynx-2.8.2, configured with --enable-prettysrc, the nice
colour scheme does not work correctly any more when the display
character set has been set to "UNICODE UTF-8". This is fixed by a
simple patch lynx282.diff.
The Lynx developers say: "For any serious use of UTF-8 screen output
with lynx, compiling with slang lib and -DSLANG_MBCS_HACK is still
recommended."
ftp://ftp.gnu.org/pub/gnu/lynx/lynx-2.8.2.tar.gz
http://lynx.browser.org/ http://www.slcc.edu/lynx/ ftp://lynx.isc.org/
4.2.3. Test pages
Some test pages for browsers can be found at the pages of Alan Wood
http://www.hclrss.demon.co.uk/unicode/#links and James Kass
http://home.att.net/~jameskass/.
4.3. Editors
4.3.1. yudit
yudit by Gaspar Sinai http://czyborra.com/yudit/ is a first-class
unicode text editor for the X Window System. It supports simultaneous
processing of many languages, input methods, conversions for local
character standards. It has facilities for entering text in all
languages with only an English keyboard, using keyboard configuration
maps.
It can be compiled in three versions: Xlib GUI, KDE GUI, or Motif GUI.
Customization is very easy. Typically you will first customize your
font. From the font menu I chose "Unicode". Then, since the command
"xlsfonts '*-*-iso10646-1'" still showed some ambiguity, I chose a
font size of 13 (to match Markus Kuhn's 13-pixel fixed font).
Next, you will customize your input method. The input methods
"Straight", "Unicode" and "SGML" are most remarkable. For details
about the other built-in input methods, look in
/usr/local/share/yudit/data/.
To make a change the default for the next session, edit your
$HOME/.yuditrc file.
The general editor functionality is limited to editing, cut&paste and
search&replace. No undo.
4.3.2. mined98
mined98 is a small text editor by Michiel Huisjes, Achim Mueller and
Thomas Wolff. http://www.inf.fu-berlin.de/~wolff/mined.html It lets
you edit UTF-8 or 8-bit encoded files, in an UTF-8 or 8-bit xterm. It
also has powerful capabilities for entering Unicode characters.
When it is running in xterm or Linux console in UTF-8 mode, you should
set the environment variable utf8_term, or call mined with the
command-line option -U.
mined lets you edit both 8-bit encoded and UTF-8 encoded files. By
default it uses an autodetection heuristic. If you don't want to rely
on heuristics, pass the command-line option -u when editing an UTF-8
file, or +u when editing an 8-bit encoded file. You can change the
interpretation at any time from within the editor: It displays the
encoding ("L:h" for 8-bit, "U:h" for UTF-8) in the menu line. Click on
the first of these characters to change it.
A few caveats:
o The Linux binary in the distribution is out of date and does not
support UTF-8. You have to rebuild a binary from the source. Then
install src/mined as /usr/local/bin/mined, and install
doc/mined.help as /usr/local/man/cat1/mined.1, so that ESC h will
find it.
o mined ignores your "stty erase" setting. When your backspace key
sends ASCII code 127, and you have set "stty erase ^?", -- these
are the ultimately correct settings -- you have to call mined with
option -B in order to get the backspace key erase a character to
the left of the cursor.
o The "Home", "End", "Delete" keys do not work.
4.3.3. vim
vim (as of version 5.4m) has some support for multi-byte locales, but
only as far as the X library has the same support, and only for
encodings with at most two bytes per character (i.e. ISO-2022
encodings). No UTF-8 support.
4.3.4. emacs
First of all, you should read the section "International Character Set
Support" (node "International") in the Emacs manual. In particular,
note that you need to start Emacs using the command
$ emacs -fn fontset-standard
so that it will use a font set comprising a lot of international char-
acters.
In the short term, the emacs-utf package
http://www.cs.ust.hk/faculty/otfried/Mule/ by Otfried Cheong provides
a "unicode-utf8" encoding to Emacs. After compiling the program
"utf2mule" and installing it somewhere in your $PATH, also install
unicode.el, muleuni-1.el, unicode-char.el somewhere, and add the lines
(setq load-path (cons "/home/user/somewhere/emacs" load-path))
(if (not (string-match "XEmacs" emacs-version))
(progn
(require 'unicode)
(if (eq window-system 'x)
(progn
(create-fontset-from-fontset-spec
"-misc-fixed-medium-r-normal-*-12-*-*-*-*-*-fontset-standard")
(create-fontset-from-fontset-spec
"-misc-fixed-medium-r-normal-*-13-*-*-*-*-*-fontset-standard")
(create-fontset-from-fontset-spec
"-misc-fixed-medium-r-normal-*-14-*-*-*-*-*-fontset-standard")
(create-fontset-from-fontset-spec
"-misc-fixed-medium-r-normal-*-15-*-*-*-*-*-fontset-standard")
(create-fontset-from-fontset-spec
"-misc-fixed-medium-r-normal-*-16-*-*-*-*-*-fontset-standard")
(create-fontset-from-fontset-spec
"-misc-fixed-medium-r-normal-*-18-*-*-*-*-*-fontset-standard")))))
to your $HOME/.emacs file. To activate any of the font sets, use the
Mule menu item "Set Font/FontSet" or Shift-down-mouse-1. Currently the
font sets with height 15 and 13 have the best Unicode coverage, due to
Markus Kuhn's 9x15 and 6x13 fonts. In order to open an UTF-8 encoded
file, you will type
M-x universal-coding-system-argument unicode-utf8 RET
M-x find-file filename RET
or
C-x RET c unicode-utf8 RET
C-x C-f filename RET
Note that this works with Emacs in windowing mode only, not in
terminal mode.
Richard Stallman plans to add integrated UTF-8 support to Emacs in the
long term.
4.3.5. xemacs
(This section is written by Gilbert Baumann.)
Here is how to teach XEmacs (20.4 configured with MULE) the UTF-8
encoding. Unfortunately you need its sources to be able to patch it.
First you need these files provided by Tomohiko Morioka:
http://turnbull.sk.tsukuba.ac.jp/Tools/XEmacs/xemacs-21.0-b55-emc-
b55-ucs.diff and http://turnbull.sk.tsukuba.ac.jp/Tools/XEmacs/xemacs-
ucs-conv-0.1.tar.gz
The .diff is a diff against the C sources. The tar ball is elisp code,
which provides lots of code tables to map to and from Unicode. As the
name of the diff file suggests it is against XEmacs-21; I needed to
help `patch' a bit. The most notable difference to my XEmacs-20.4
sources is that file-coding.[ch] was called mule-coding.[ch].
For those unfamilar with the XEmacs-MULE stuff (as I am) a quick
guide:
What we call an encoding is called by MULE a `coding-system'. The most
important commands are:
M-x set-file-coding-system
M-x set-buffer-process-coding-system [comint buffers]
and the variable `file-coding-system-alist', which guides `find-file'
to guess the encoding used. After stuff was running, the very first
thing I did was this.
This code looks into the special mode line introduced by -*- somewhere
in the first 600 bytes of the file about to opened; if now there is a
field "Encoding: xyz;" and the xyz encoding ("coding system" in Emacs
speak) exists, choose that. So now you could do e.g.
;;; -*- Mode: Lisp; Syntax: Common-Lisp; Package: CLEX; Encoding: utf-8; -*-
and XEmacs goes into utf-8 mode here.
Atfer everything was running I defined \u03BB (greek lambda) as a
macro like:
(defmacro \u03BB (x) `(lambda .,x))
4.3.6. nedit
4.3.7. xedit
In theory, xedit should be able to edit UTF-8 files if you set the
locale accordingly (see above), and add the line "Xedit*international:
true" to your $HOME/.Xdefaults file. In practice, it will recognize
UTF-8 encoding of non-ASCII characters, but will display them as
sequences of "@" characters.
4.3.8. axe
In theory, axe should be able to edit UTF-8 files if you set the
locale accordingly (see above), and add the line "Axe*international:
true" to your $HOME/.Xdefaults file. In practice, it will simply dump
core.
4.3.9. pico
4.3.10. TeX
The teTeX 0.9 (and newer) distribution contains an Unicode adaptation
of TeX, called Omega (http://www.gutenberg.eu.org/omega/,
ftp://ftp.ens.fr/pub/tex/yannis/omega), but can someone point me to a
tutorial for using this system?
Other maybe related links: http://www.dante.de/projekte/nts/NTS-
FAQ.html, ftp://ftp.dante.de/pub/tex/language/chinese/CJK/.
4.4. Mailers
MIME: RFC 2279 defines UTF-8 as a MIME charset, which can be
transported under the 8bit, quoted-printable and base64 encodings. The
older MIME UTF-7 proposal (RFC 2152) is considered to be deprecated
and should not be used any further.
Mail clients released after January 1, 1999, should be capable of
sending and displaying UTF-8 encoded mails, otherwise they are
considered deficient. But these mails have to carry the MIME labels
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Simply piping an UTF-8 file into "mail" without caring about the MIME
labels will not work.
Mail client implementors should take a look at http://www.imc.org/imc-
intl/ and http://www.imc.org/mail-i18n.html.
Now about the individual mail clients (or "mail user agents"):
4.4.1. pine
The situation for an unpatched pine version 4.10 is as follows.
Pine does not do character set conversions. But it allows you to view
UTF-8 mails in an UTF-8 text window (Linux console or xterm).
Normally, Pine will warn about different character sets each time you
view an UTF-8 encoded mail. To get rid of this warning, choose S
(setup), then C (config), then change the value of "character-set" to
UTF-8. This option will not do anything, except to reduce the
warnings, as Pine has no built-in knowledge of UTF-8.
Also note that Pine's notion of Unicode characters is pretty limited:
It will display Latin and Greek characters, but not other kinds of
Unicode characters.
A patch by Robert Brady http://www.ents.susu.soton.ac.uk/~robert/pine-
utf8-0.1.diff adds UTF-8 support to Pine. With this patch, it decodes
and prints headers and bodies properly. The patch depends on the GNOME
libunicode http://cvs.gnome.org/lxr/source/libunicode/.
However, alignment remains broken in many places; replying to a mail
does not cause the character set to be converted as appropriate; and
the editor, pico, cannot deal with multibyte characters.
4.4.2. kmail
kmail (as of KDE 1.0) does not support UTF-8 mails at all.
4.4.3. Netscape Communicator
Netscape Communicator's Messenger can send and display mails in UTF-8
encoding, but it needs a little bit of manual user intervention.
To send an UTF-8 encoded mail: After opening the "Compose" window, but
before starting to compose the message, select from the menu "View ->
Character Set -> Unicode (UTF-8)". Then compose the message and send
it.
When you receive an UTF-8 encoded mail, Netscape unfortunately does
not display it in UTF-8 right away, and does not even give a visual
clue that the mail was encoded in UTF-8. You have to manually select
from the menu "View -> Character Set -> Unicode (UTF-8)".
For displaying UTF-8 mails, Netscape uses different fonts. You can
adjust your font settings in the "Edit -> Preferences -> Fonts"
dialog; choose the "Unicode" font category.
4.4.4. emacs (rmail, vm)
4.5. Other text-mode applications
4.5.1. less
Get ftp://ftp.gnu.org/pub/gnu/less/less-340.tar.gz and apply the patch
less-340-utf-2.diff by Robert Brady <rwb197@ecs.soton.ac.uk>. Then
set the environment variable LESSCHARSET:
$ export LESSCHARSET=utf-8
If you also have a LESSKEY environment variable set, also make sure
that the file it points to does not define LESSCHARSET. If necessary,
regenerate this file using the `lesskey' command, or unset the LESSKEY
environment variable.
4.5.2. expand, wc
Get the GNU textutils-2.0 and apply the patch textutils-2.0.diff, then
configure, add "#define HAVE_MBRTOWC 1", "#define HAVE_FGETWC 1",
"#define HAVE_FPUTWC 1" to config.h. In src/Makefile, modify CFLAGS
and LDFLAGS so that they include the directories where libutf8 is
installed. Then rebuild.
4.5.3. col, colcrt, colrm, column, rev, ul
Get the util-linux-2.9y package, configure it, then define
ENABLE_WIDECHAR in defines.h, change the "#if 0" to "#if 1" in
lib/widechar.h. In text-utils/Makefile, modify CFLAGS and LDFLAGS so
that they include the directories where libutf8 is installed. Then
rebuild.
4.5.4. figlet
figlet 2.2 has an option for UTF-8 input: "figlet -C utf8"
4.5.5. kermit
The serial communications program C-Kermit
http://www.columbia.edu/kermit/, in versions 7.0beta10 or newer,
understands the file and transfer encodings UTF-8 and UCS-2, and
understands the terminal encoding UTF-8. Documentation of these
features can be found in
ftp://kermit.columbia.edu/kermit/test/text/ckermit2.txt.
4.6. Other X11 applications
X11 Xlib kann leider noch kein UTF-8 locale, das msste auch noch
dringend mal gemacht werden.
5. Making your programs Unicode aware
5.1. C/C++
The C `char' type is 8-bit and will stay 8-bit because it denotes the
smallest addressable data unit. Various facilities are available:
5.1.1. For normal text handling
The ISO/ANSI C standard contains, in an amendment which was added in
1995, a "wide character" type `wchar_t', a set of functions like those
found in <string.h> and <ctype.h> (declared in <wchar.h> and
<wctype.h>, respectively), and a set of conversion functions between
`char *' and `wchar_t *' (declared in <stdlib.h>).
Good references for this API are
o the GNU libc-2.1 manual, chapters 4 "Character Handling" and 6
"Character Set Handling",
o the manual pages man-mbswcs.tar.gz,
o the Dinkumware C library reference
http://www.dinkumware.com/htm_cl/,
o the OpenGroup's Single Unix specification http://www.UNIX-
systems.org/online.html.
Advantages of using this API:
o It's a vendor independent standard.
o The functions do the right thing, depending on the user's locale.
All a program needs to call is setlocale(LC_ALL,"");.
Drawbacks of this API:
o Some of the functions are not multithread-safe, because they keep a
hidden internal state between function calls.
o There is no first-class locale datatype. Therefore this API cannot
reasonably be used for anything that needs more than one locale or
character set at the same time.
o The OS support for this API is not good on most OSes.
5.1.1.1. Portability notes
A `wchar_t' may or may not be encoded in Unicode; this is platform and
sometimes also locale dependent. A multibyte sequence `char *' may or
may not be encoded in UTF-8; this is platform and sometimes also
locale dependent.
In detail, here is what the Single Unix specification says about the
`wchar_t' type: All wide-character codes in a given process consist of
an equal number of bits. This is in contrast to characters, which can
consist of a variable number of bytes. The byte or byte sequence that
represents a character can also be represented as a wide-character
code. Wide-character codes thus provide a uniform size for
manipulating text data. A wide-character code having all bits zero is
the null wide-character code, and terminates wide-character strings.
The wide-character value for each member of the Portable Character Set
(i.e. ASCII) will equal its value when used as the lone character in
an integer character constant. Wide-character codes for other
characters are locale- and implementation-dependent. State shift bytes
do not have a wide-character code representation.
One particular consequence is that in portable programs you shouldn't
use non-ASCII characters in string literals. That means, even though
you know the Unicode double quotation marks have the codes U+201C and
U+201D, you shouldn't write a string literal L"\u201cHello\u201d, he
said" or "\xe2\x80\x9cHello\xe2\x80\x9d, he said" in C programs.
Instead, use GNU gettext, write it as gettext("'Hello', he said"), and
create a message database en.UTF-8.po which translates "'Hello', he
said" to "\u201cHello\u201d, he said".
Here is a survey of the portability of the ISO/ANSI C facilities on
various Unix flavours. GNU glibc-2.2 will support all of it, but for
now we have the following picture.
GNU glibc-2.0.x, glibc-2.1.x
o <wchar.h> and <wctype.h> exist.
o Has wcs/mbs functions, but no fgetwc/fputwc/wprintf.
o No UTF-8 locale.
o mbrtowc returns EILSEQ for bytes >= 0x80.
Solaris 2.7
o <wchar.h> and <wctype.h> exist.
o Has wcs/mbs functions, fgetwc/fputwc/wprintf, everything.
o Has the following UTF-8 locales: en_US.UTF-8, de.UTF-8,
es.UTF-8, fr.UTF-8, it.UTF-8, sv.UTF-8.
o mbrtowc returns EILSEQ for bytes >= 0x80.
OSF/1 4.0d
o <wchar.h> and <wctype.h> exist.
o Has wcs/mbs functions, fgetwc/fputwc/wprintf, everything.
o Has an add-on universal.utf8@ucs4 locale, see "man 5 unicode".
o mbrtowc does not know about UTF-8.
Irix 6.5
o <wchar.h> and <wctype.h> exist.
o Has wcs/mbs functions and fgetwc/fputwc, but not wprintf.
o Has no multibyte locales.
o Has only a dummy definition for mbstate_t.
o Doesn't have mbrtowc.
HP-UX 11.00
o <wchar.h> exists, <wctype.h> does not.
o Has wcs/mbs functions and fgetwc/fputwc, but not wprintf.
o Has a C.utf8 locale.
o Doesn't have mbstate_t.
o Doesn't have mbrtowc.
AIX 4.2
o <wchar.h> exists, <wctype.h> does not - instead use <ctype.h>
and <wchar.h>.
o Has wcs/mbs functions and fgetwc/fputwc, but not wprintf.
o Has the following UTF-8 locales: ET_EE.UTF-8, LT_LT.UTF-8,
LV_LV.UTF-8, ZH_CN.UTF-8.
o Doesn't have mbstate_t.
o Doesn't have mbrtowc.
As a consequence, I recommend to use the restartable and multithread-
safe wcsr/mbsr functions, forget about those systems which don't have
them (Irix, HP-UX, AIX), and use the UTF-8 locale plug-in
libutf8_plug.so (see below) on those systems which permit you to
compile programs which use these wcsr/mbsr functions (Linux, Solaris,
OSF/1).
A similar advice, given by Sun in http://www.sun.com/software/white-
papers/wp-unicode/, section "Internationalized Applications with
Unicode", is:
To properly internationalize an application, use the following
guidelines:
1. Avoid direct access with Unicode. This is a task of the platform's
internationalization framework.
2. Use the POSIX model for multibyte and wide-character interfaces.
3. Only call the APIs that the internationalization framework provides
for language and cultural-specific operations.
4. Remain code-set independent.
If, for some reason, in some piece of code, you really have to assume
that `wchar_t' is Unicode (for example, if you want to do special
treatment of some Unicode characters), you should make that piece of
code conditional upon the result of is_locale_utf8(). Otherwise you
will mess up your program's behaviour in different locales or other
platforms. The function is_locale_utf8 is declared in utf8locale.h and
defined in utf8locale.c.
5.1.1.2. The libutf8 library
A portable implementation of the ISO/ANSI C API, which supports 8-bit
locales and UTF-8 locales, can be found in libutf8-0.5.2.tar.gz.
Advantages:
o Unicode UTF-8 support now, portably, even on OSes whose multibyte
character support does not work or which don't have multibyte/wide
character support at all.
o The same binary works in all OS supported 8-bit locales and in
UTF-8 locales.
o When an OS vendor adds proper multibyte character support, you can
take advantage of it by simply recompiling without -DHAVE_LIBUTF8
compiler option.
5.1.1.3. The Plan9 way
The Plan9 operating system, a variant of Unix, uses UTF-8 as character
encoding in all applications. Its wide character type is called
`Rune', not `wchar_t'. Parts of its libraries, written by Rob Pike and
Howard Trickey, are available at
ftp://ftp.cdrom.com/pub/netlib/research/9libs/9libs-1.0.tar.gz.
Another similar library, written by Alistair G. Crooks, is
ftp://ftp.cdrom.com/pub/NetBSD/packages/distfiles/libutf-2.10.tar.gz.
In particular, each of these libraries contains an UTF-8 aware regular
expression matcher.
Drawback of this API:
o UTF-8 is compiled in, not optional. Programs compiled in this
universe lose support for the 8-bit encodings which are still
frequently used in Europe.
5.1.2. For graphical user interface
The Qt-2.0 library http://www.troll.no/ contains a fully-Unicode
QString class. You can use the member functions QString::utf8 and
QString::fromUtf8 to convert to/from UTF-8 encoded text. The
QString::ascii and QString::latin1 member functions should not be used
any more.
5.1.3. For advanced text handling
The previously mentioned libraries implement Unicode aware versions of
the ASCII concepts. Here are libraries which deal with Unicode
concepts, such as titlecase (a third letter case, different from
uppercase and lowercase), distinction between punctuation and symbols,
canonical decomposition, combining classes, canonical ordering and the
like.
ucdata-1.9
The ucdata library by Mark Leisher
http://crl.nmsu.edu/~mleisher/ucdata.html deals with character
properties, case conversion, decomposition, combining classes.
ICU
IBMs Classes for Unicode
http://www.alphaworks.ibm.com/tech/icu/. A very comprehensive
internationalization library featuring Unicode strings, resource
bundles, number formatters, date/time formatters, message
formatters, collation and more. Lots of supported locales.
Portable to Unix and Win32, but compiles out of the box only on
Linux libc6, not libc5.
libunicode
The GNOME libunicode library
http://cvs.gnome.org/lxr/source/libunicode/ by Tom Tromey and
others. It covers character set conversion, character
properties, decomposition.
5.1.4. For conversion
Two conversion libraries, which support UTF-8 and a large number of
8-bit character sets, are available:
The iconv implementation by Ulrich Drepper, contained in the GNU
glibc-2.1.1. ftp://ftp.gnu.org/pub/gnu/glibc/glibc-2.1.1.tar.gz
Advantages:
o iconv is POSIX standardized, programs using iconv to convert
from/to UTF-8 will also run under Solaris. However, the names for
the character sets differ between platforms. For example, "EUC-JP"
under glibc is "eucJP" under HP-UX. (The official IANA name for
this character set is "EUC-JP", so it's clearly a HP-UX
deficiency.)
o No additional library needed.
librecode by Francois Pinard
ftp://ftp.gnu.org/pub/gnu/recode/recode-3.5.tar.gz.
Advantages:
o Support for transliteration, i.e. conversion of non-ASCII
characters to sequences of ASCII characters in order to preserve
readability by humans, even when a lossless transformation is
impossible.
Drawbacks:
o Non-standard API.
5.1.5. Other approaches
libutf-8
libutf-8 by G. Adam Stanislav <adam@whizkidtech.net> contains a
few functions for on-the-fly conversion from/to UTF-8 encoded
`FILE*' streams.
http://www.whizkidtech.net/i18n/libutf-8-1.0.tar.gz
Advantages:
o Very small.
Drawbacks:
o Non-standard API.
o UTF-8 is compiled in, not optional. Programs compiled with this
library lose support for the 8-bit encodings which are still
frequently used in Europe.
o Installation is nontrivial: Makefile needs tweaking, not
autoconfiguring.
5.2. Java
Java has Unicode support built into the language. The type `char'
denotes a Unicode character, and the `java.lang.String' class denotes
a string built up from Unicode characters.
Java can display any Unicode characters through its windowing system
AWT, provided that 1. you set the Java system property "user.language"
appropriately, 2. the /usr/lib/java/lib/font.properties.language font
set definitions are appropriate, and 3. the fonts specified in that
file are installed. For example, in order to display text containing
japanese characters, you would install japanese fonts and run "java
-Duser.language=ja ...". You can combine font sets: In order to
display western european, greek and japanese characters
simultaneously, you would create a combination of the files
"font.properties" (covers ISO-8859-1), "font.properties.el" (covers
ISO-8859-7) and "font.properties.ja" into a single file. ??This is
untested??
The interfaces java.io.DataInput and java.io.DataOutput have methods
called `readUTF' and `writeUTF' respectively. But note that they don't
use UTF-8; they use a modified UTF-8 encoding: the NUL character is
encoded as the two-byte sequence 0xC0 0x80 instead of 0x00, and a 0x00
byte is added at the end. Encoded this way, strings can contain NUL
characters and nevertheless need not be prefixed with a length field -
the C <string.h> functions like strlen() and strcpy() can be used to
manipulate them.
5.3. Lisp
The Common Lisp standard specifies two character types: `base-char'
and `character'. It's up to the implementation to support Unicode or
not. The language also specifies a keyword argument `:external-
format' to `open', as the natural place to specify a character set or
encoding.
Among the free Common Lisp implementations, only CLISP
http://clisp.cons.org/ supports Unicode. You need a CLISP version from
July 1999 or newer.
ftp://clisp.cons.org/pub/lisp/clisp/source/clispsrc.tar.gz. The types
`base-char' and `character' are both equivalent to 16-bit Unicode.
The encoding used for file or socket/pipe I/O can be specified through
the `:external-format' argument. The encodings used for tty I/O and
the default encoding for file/socket/pipe I/O are locale dependent.
Among the commercial Common Lisp implementations, only Eclipse
http://www.elwood.com/eclipse/eclipse.htm supports Unicode. See
http://www.elwood.com/eclipse/char.htm. The type `base-char' is
equivalent to ISO-8859-1, and the type `character' contains all
Unicode characters. The encoding used for file I/O can be specified
through a combination of the `:element-type' and `:external-format'
arguments to `open'. Limitations: Character attribute functions are
locale dependent. Source and compiled source files cannot contain
Unicode string literals.
The commercial Common Lisp implementation Allegro CL does not support
Unicode yet, but Erik Naggum is working on it.
5.4. Ada95
Ada95 was designed for Unicode support and the Ada95 standard library
features special ISO 10646-1 data types Wide_Character and
Wide_String, as well as numerous associated procedures and functions.
The GNU Ada95 compiler (gnat-3.11 or newer) supports UTF-8 as the
external encoding of wide characters. This allows you to use UTF-8 in
both source code and application I/O. To activate it in the
application, use "WCEM=8" in the FORM string when opening a file, and
use compiler option "-gnatW8" if the source code is in UTF-8. See the
GNAT and Ada95 reference manuals for details.