Table of Contents
The international support for the application software is done in 2 steps:
Multilingualization (m17n): To make software independent of the particular locale.
Localization (l10n): To configure multilingualized software to the particular locale.
Here, I18N stands for "internationalization" and L10N stands for "localization". (There are 18 and 10 letters between I and N or L and N.)
The modern software such as Gnome and KDE which are written to handle UTF-8 data and to provide their message through the gettext
(1) infrastructure are multilingualized and can be localized simply by setting pertinent environment variables to the appropriate locale if the corresponding translated message packages are installed.
The simplest representation of the text data is ASCII which is sufficient for English and uses less than 127 characters (representable with 7 bits). In order to support much more characters for the international support, many character encoding systems have been invented. The modern and sensible encoding system is UTF-8 which can handle practically all the characters known to the human (see: Section 9.3.1, “Basics of encoding”).
See Introduction to i18n for details.
The international hardware support is enabled with localized hardware configuration data.
The Debian system can be configured to work with many international keyboard arrangements:
Table 9.1. List of keyboard reconfiguration methods.
environment |
command |
---|---|
Linux console |
|
X Window |
|
This will support keyboard input for accented characters of many European languages with its dead-key function. For Asian languages, you need more complicated input method support such as scim
discussed next.
Setup of multilingual input for the Debian system is simplified by using the SCIM family of packages with the im-switch
package. The list of SCIM packages are:
Table 9.2. List of input method supports with scim.
package |
popcon |
locale |
---|---|---|
scim-anthy |
V:0.2, I:0.7 |
Japanese |
scim-canna |
V:0.05, I:0.3 |
, , |
scim-skk |
V:0.04, I:0.3 |
, , |
scim-prime |
V:0.04, I:0.3 |
, , |
scim-tables-ja |
I:0.6 |
, , (not useful) |
scim-tables-zh |
I:1.2 |
Chinese (for zh_*) |
scim-pinyin |
V:0.2, I:1.1 |
, , (for zh_CN) |
scim-chewing |
V:0.09, I:0.8 |
, , (for zh_TW) |
scim-hangul |
V:0.04, I:0.10 |
Korean |
scim-tables-ko |
I:0.08 |
, , |
scim-thai |
V:0.01, I:0.04 |
Thai |
scim-m17n |
V:0.06, I:0.17 |
Multilingual: Indic, Arabic and others |
scim-tables-additional |
I:0.2 |
, , |
scim-uim |
V:0.04, I:0.3 |
, , |
The kinput2
method and other locale dependent Asian classic input methods still exist but are not recommended for the modern UTF-8 X environment. The uim
tool chain is an alternative approach for the international input method for the modern UTF-8 X environment which is also capable for non-X environment.
I find the Japanese input method started under English environment (en_US.UTF-8
) very useful. Here is how I did it with SCIM.
Install the Japanese input tool package scim-anthy
with its recommended packages such as im-switch
.
Execute "im-switch -c
" from user's shell and select "scim".
Relogin to user's account.
Verify setting by "im-switch -l
".
Setup input method and mode by right clicking GUI toolbar. (You can reduce menu choice of input method)
Start SCIM input method by CTRL-SPACE
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Note |
---|---|
In order to start SCIM under the non-CJK and non-en_US locale, you need to add list of those locales in UTF-8 to the |
/SupportedUnicodeLocales = en_US.UTF-8,en_GB.UTF_8,fr_FR.UTF-8
Please note:
The im-switch
command behaves differently if command is executed from root or not.
Input method started by im-switch
depends on the locale.
Use of new immodule mechanism (via GTK_IM_MODULE) may cause instability during the library transition in unstable
.
For the detail of setup, see /usr/share/doc/im-switch/README.Debian.gz
, /usr/share/doc/scim/README.Debian.gz
or /usr/share/doc/uim/README.Debian.gz
. Here key points are described.
If you wish to input without going through XIM, set XMODIFIERS
value to "none" while starting a program. This may be the case if you use Japanese input infrastructure egg
on emacs
. From shell, execute as:
$ XMODIFIERS=none emacs
In order to adjust the command executed by the Debian menu, place customized configuration in /etc/menu
following method described in /usr/share/doc/menu/html
.
Linux console can only display limited characters. (You need to use special terminal program such as jfbterm
to display non-European languages on the non-X console.)
X Window can display any characters in the UTF-8 as long as required font data exists. (The encoding of the original font data is taken care by the X Window system and transparent to the user.)
The following will focus on the locale for applications run under X Window environment started from the gdm
.
The environment variable "LANG=xx_YY.ZZZZ
" sets the locale to language code "xx
", country code "yy
", and encoding "ZZZZ
" (see: Section 2.5.1.1, “LANG variable”).
Current Debian system normally sets the locale as "LANG=xx_YY.UTF-8
". This uses the UTF-8 encoding with the Unicode character set. This UTF-8 encoding system is a multibyte code system and uses code points smartly. The ASCII data, which consist only with 7-bit range codes, are always valid UTF-8 data consisting only with 1 byte per character.
Previous Debian system used to set the locale as "LANG=C
" or "LANG=xx_YY
".
The ASCII character set is used for "LANG=C
" or "LANG=POSIX
".
The traditional encoding system in Unix is used for "LANG=xx_YY
" (see: Table 2.18, “ The 3 parts of locale value. ”).
Actual traditional encoding system used for "LANG=xx_YY
" can be identified by checking "/usr/share/i18n/SUPPORTED
". For example, "en_US
" uses "ISO-8859-1
" encoding and "fr_FR@euro
" uses "ISO-8859-15
" encoding.
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Tip |
---|---|
For meaning of encoding values, see: Table 12.2, “ List of encoding values and their usage. ” . |
The UTF-8 encoding is the modern and sensible text encoding system for I18N and enables to represent Unicode characters, i.e., practically all characters known to human. UTF stands for Unicode Transformation Format (UTF) schemes.
I recommend to use UTF-8 locale for your desktop, e.g., "LANG=en_US.UTF-8
". The first part of the locale determines messages presented by applications. For example, gedit
(1) (text editor for the GNOME Desktop) under "LANG=fr_FR.UTF-8
" locale can display and edit Chinese character text data while presenting menus in French, as long as required fonts and input methods are installed.
I also recommend to set the locale only using LANG
environment variable. I do not see much benefit of setting a complicated combination of LC_*
variables (see locale
(1) manpage) under UTF-8 locale.
Even plain English text may contain non-ASCII characters, e.g. left and right quotation marks are not available in ASCII:
“double quoted text” ‘single quoted text’
When ASCII plain text data is converted to UTF-8 one, it has exactly the same content and size as the original ASCII one. So you loose nothing by deploying UTF-8 locale.
Some programs consume more memory after supporting I18N. This is because they are coded to use UTF-32(UCS4) internally to support Unicode for speed optimization and consume 4 bytes per each ASCII character data independent of locale selected. Again, you loose nothing by deploying UTF-8 locale.
The vendor specific old non-UTF-8 encoding systems tend to have minor but annoying differences on some characters such as graphic ones for many countries. The deployment of the UTF-8 system by the modern OSs practically solved these conflicting encoding issues.
In order for the system to access a particular locale, the locale data must be compiled from the locale database. (The Debian system does not come with all available locales pre-compiled unless you installed the locales-all
package.) The full list of supported locales available for compiling are listed in /usr/share/i18n/SUPPORTED
. This lists all the proper locale names. The following will list all the available UTF-8 locales already compiled to the binary form:
$ locale -a
The following command execution will reconfigure locale
package:
to update the list of available locales,
to compile them into the binary form, and
to set the system wide default locale value in the /etc/defaults/locale
for use by PAM (see: Section 5.5, “PAM and NSS”).
# dpkg-reconfigure locales
The list of available locale should include "en_US.UTF-8
" and all the interesting languages with "UTF-8
".
The recommended default locale is "en_US.UTF-8
" for US English. For other languages, please make sure to chose locale with "UTF-8
". Any one of these settings can handle any international characters.
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Note |
---|---|
Although setting locale to " |
The environment variable LANG
is:
set initially by some display manager such as gdm
for all X programs,
changed by the X session startup code via $HOME/.xsessionrc
for all X programs (lenny feature),
set initially by the PAM mechanism of the login
for the local Linux console programs,
set initially by the PAM mechanism of the ssh
for the remote console programs, or
changed by the shell startup code, e.g. $HOME/.bashrc
, for all console programs.
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Tip |
---|---|
It is good idea to install system wide default locale as " |
You can chose specific locale only under X Window irrespective of your system wide default locale. This should provide your best desktop experience with stability.
This way, you can always access functioning character terminal with readable messages even when X Window system is not working. This becomes essential for languages which use non-roman characters such as Chinese, Japanese, and Korean.
For gdm
, you can select different locale for the X session from its menu independent of the system default locale value in the /etc/defaults/locale
.
You can set the locale of the X session manager and the value for the default locale permanently using PAM customization (see: Section 5.5, “PAM and NSS”) as follows. (There may be another way available as the improvement of X session manager package but please read following as the generic and basic method of setting the locale.)
First, change the following line defining language environment variable in its PAM configuration file, such as /etc/pam.d/gdm
:
auth required pam_env.so read_env=1 envfile=/etc/default/locale
into
auth required pam_env.so read_env=1 envfile=/etc/default/locale-x
Then create a /etc/defaults/locale-gdm
file with "-rw-r--r-- 1 root root
" permission containing, eg. for Japanese message:
LANG="ja_JP.UTF-8"
and keep the default /etc/defaults/locale
file for other programs being:
LANG="en_US.UTF-8"
This is the most generic technique to customize locale.
Alternatively for this case, you may simply change locale using the $HOME/.xsessionrc
file.
For cross platform data exchanges (see Section 11.1.10, “Removable mass storage device”), you may need to mount some file system with particular encodings. For example, the mount
(8) command for vfat filesystem assumes CP437 if used without option. You need to provide explicit mount option to use UTF-8 or CP932 for filenames.
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Note |
---|---|
When auto-mounting a hot-pluggable USB memory stick under modern desktop environment such as Gnome, you may provide such mount option by right clicking the icon on the desktop, click "Drive" tab, click to expand "Setting", and entering "utf8" to "Mount options:". The next time this memory stick is mounted, mount with UTF-8 is enabled. |
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Note |
---|---|
If you are upgrading system or moving disk drives from older non-UTF-8 system, file names with non-ASCII characters may be encoded in the historic and deprecated encodings such as ISO-8859-1 or eucJP. Please seek help of text conversion tools to convert them to UTF-8. See: Section 12.1, “Text data conversion tools” . |
Samba uses Unicode for newer clients (Windows NT, 200x, XP) but uses CP850 as default for older clients (DOS and Windows 9x/Me clients). This default for older clients can be changed using "dos charset
" in the /etc/samba/smb.conf
file, e.g., to CP932 for Japanese.
Translations exist for many of the text messages and documents that are displayed in the Debian system, such as error messages, standard program output, menus, and manual pages. GNU gettext(1) command tool chain is used as the backend tool for most translation activities.
The aptitude
list under "Tasks" -> "Localization" provide extensive list of useful binary packages which add localized messages to applications and provide translated documentation.
For example, you can obtain the localized message for manpage by installing the manpages-<LANG>
. To read the Italian-language manpage for <programname>, execute
LANG=it_IT.UTF-8 man <programname>
to read it from /usr/share/man/it/
.
The sort order of characters with sort
(1) is affected by the language choice of the locale. Spanish and English locale sort differently.
The date format of ls
(1) is affected by the locale. The date format of "LANG=C ls -l
" and "LANG=en_US.UTF-8
" are different.
Number punctuation are different for locale. For example, in English locale, one thousand one point one is displayed as "1,000.1
" while in German locale, it is displayed as "1.000,1
". You see this difference in spreadsheet program.