Chapter 8. I18N and L10N

“double quoted text” is not "double quoted ASCII"
‘single quoted text’ is not 'single quoted ASCII'

In order to support more characters, many character sets and encoding systems have been used to support many languages (see Table 11.2, “List of encoding values and their usage”).

Unicode character set can represent practically all characters known to human with 21 bit code point range (i.e., 0 to 10FFFF in hexadecimal notation).

Text encoding system UTF-8 fits Unicode code points into a sensible 8 bit data stream mostly compatible with the ASCII data processing system. This makes UTF-8 the modern preferred choice. UTF stands for Unicode Transformation Format. 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.

Under UTF-8 locale with the compatible application program, you can display and edit any foreign language text data as long as required fonts and input methods are installed and enabled. For example under "LANG=fr_FR.UTF-8" locale, gedit(1) (text editor for the GNOME desktop) can display and edit Chinese character text data while presenting menus in French.

	Tip
	Both the new standard "en_US.UTF-8" locale and the old standard "C"/"POSIX" locale use the standard US English message, they have subtle differences in sorting order etc. If you want to handle not only ASCII characters but also handle all UTF-8 encoded characters gracefully while maintaining the old "C" local behavior, use the non-standard "C.UTF-8" locale on Debian.

	Note
	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.

# dpkg-reconfigure locales

The system wide default locale value set in "/etc/default/locale" may be overridden by the GUI configuration for GUI applications.

	Note
	Actual traditional encoding system can be identified by "/usr/share/i18n/SUPPORTED". Thus, the "LANG=en_US" is "LANG=en_US.ISO-8859-1".

The locales-all package comes with pre-compiled locale data for all locale data. Since it doesn't create "/etc/default/locale", you may still need to install the locales package, too.

	Tip
	The locales package of some Debian derivative distributions come with pre-compiled locale data for all locale data. You need to install both locales and locales-all packages on Debian to emulate such system environment.

For cross platform data exchanges (see Section 10.1.7, “Removable storage device”), you may need to mount some filesystem with particular encodings. For example, mount(8) for vfat filesystem assumes CP437 if used without option. You need to provide explicit mount option to use UTF-8 or CP932 for filenames.

	Note
	When auto-mounting a hot-pluggable USB flash drive 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 USB flash drive is mounted, mount with UTF-8 is enabled.

	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 11.1, “Text data conversion tools”.

Samba uses Unicode for newer clients (Windows NT, 200x, XP) but uses CP850 for older clients (DOS and Windows 9x/Me) as default. 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.

Under "Tasks" → "Localization" aptitude(8) provides an 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 package. To read the Italian-language manpage for programname from "/usr/share/man/it/", execute as the following.

LANG=it_IT.UTF-8 man programname

GNU gettext can accommodate priority list of translation languages with $LANGUAGE environment variable. For example:

 $ export LANGUAGE="pt:pt_BR:es:it:fr"

For more, see info gettext and read the section "The LANGUAGE variable".

The date format of ls(1) is affected by the locale (see Section 9.3.4, “Customized display of time and date”).

The date format of date(1) is affected by the locale. For example:

 $ unset LC_ALL
 $ LANG=en_US.UTF-8 date
Thu Dec 24 08:30:00 PM JST 2023
 $ LANG=en_GB.UTF-8 date
Thu 24 Dec 20:30:10 JST 2023
 $ LANG=es_ES.UTF-8 date
jue 24 dic 2023 20:30:20 JST
 $ LC_TIME=en_DK.UTF-8 date
2023-12-24T20:30:30 JST

Number punctuation are different for locales. For example, in English locale, one thousand point one is displayed as "1,000.1" while in German locale, it is displayed as "1.000,1". You may see this difference in spreadsheet program.

Each detail feature of "$LANG" environment variable may be overridden by setting "$LC_*" variables. These environment variables can be overridden again by setting "$LC_ALL" variable. See locale(7) manpage for the details. Unless you have strong reason to create complicated configuration, please stay away from them and use only "$LANG" variable set to one of the UTF-8 locales.

# dpkg-reconfigure keyboard-configuration

For the Linux console and the X Window system, this updates configuration parameters in "/etc/default/keyboard". Many non-ASCII characters including accented characters used by many European languages can be made available with dead key, AltGr key, and compose key.

	Note
	If ibus is active, your classic X keyboard configuration by the setxkbmap may be overridden by ibus even under classic X-based desktop environment. You can disable installed ibus using im-config to set input method to "None". For more, see Debian Wiki on keyboard.

Unlike the X Window protocol, the Wayland core protocol doesn't even support the input of accented characters. Popular Wayland Compositors, such as Mutter for GNOME or KWin for KDE, implement extension protocols such as the text-input-unstable-v3 for the text input (see "current Wayland protocols and their support status").

The text-input-unstable-v3 protocol works well with Input methods for Wayland (see "Wayland input method project post-mortem").

The list of IBus and its plugin packages are the following.

The Fcitx (version 5) input method framework is popular with Chinese users and compatible with "ibus".

The list of "fcitx5" and its plugin packages are the following.

# dpkg-reconfigure console-setup

For the Linux console and the X Window system, this updates configuration parameters in "/etc/default/console-setup". This also configures the Linux console font. Many non-ASCII characters including accented characters used by many European languages can be made available with dead key, AltGr key, and compose key.

There are several components to configure character console and ncurses(3) system features.

If the terminfo entry for xterm doesn't work with a non-Debian xterm, change your terminal type, "$TERM", from "xterm" to one of the feature-limited versions such as "xterm-r6" when you log in to a Debian system remotely. See "/usr/share/doc/libncurses5/FAQ" for more. "dumb" is the lowest common denominator for "$TERM".

Under the East Asian locale, the box drawing, Greek, and Cyrillic characters may be displayed wider than your desired width to cause the unaligned terminal output (see Unicode Standard Annex #11, 4.2 Ambiguous Characters).

You can work around this problem: