第 8 章 I18N 和 L10N

Keyboard                               Application
   |                                        ^
   |                                        |
   +-> Linux kernel -> Input method -> Gtk, Qt, or X

Setup of multilingual input for the Debian system is simplified by using the IBus family of packages with the im-config package. The list of IBus packages are the following.

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 SCIM and uim tool chains are an slightly older approach for the international input method for the modern UTF-8 X environment.

The environment variable "LANG=xx_YY.ZZZZ" sets the locale to language code "xx", country code "yy", and encoding "ZZZZ" (see 第 1.5.2 节 ““$LANG”变量”).

The 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.

The previous Debian system used to set the locale as "LANG=C" or "LANG=xx_YY" (without ".UTF-8").

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.

	提示
	For meaning of encoding values, see 表 11.2 “List of encoding values and their usage”.

Unicode character set can represent practically all characters known to human with code point range from 0 to 10FFFF in hexadecimal notation. Its storage requires at least 21 bits.

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

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 the "$LANG" environment variable. I do not see much benefit of setting a complicated combination of "LC_*" variables (see locale(1)) under UTF-8 locale.

Even plain English text may contain non-ASCII characters, e.g. slightly curly left and right quotation marks are not available in ASCII.

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

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.

$ locale -a | grep utf8

# 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.

	注意
	Although setting locale to "C" uses US English message, it handles only ASCII characters.

You can chose specific locale only under X Window irrespective of your system wide default locale using PAM customization (see 第 4.5 节 “PAM and NSS”) as follows.

This environment should provide you with your best desktop experience with stability. You have access to the functioning character terminal with readable messages even when the X Window System is not working. This becomes essential for languages which use non-roman characters such as Chinese, Japanese, and Korean.

	注意
	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. For gdm3(1), I know you can select the locale of X session via its memu.

The following line defines file location of the language environment in the PAM configuration file, such as "/etc/pam.d/gdm3.

auth    required        pam_env.so read_env=1 envfile=/etc/default/locale

Change this to the following.

auth    required        pam_env.so read_env=1 envfile=/etc/default/locale-x

For Japanese, create a "/etc/default/locale-x" file with "-rw-r--r-- 1 root root" permission containing the following.

LANG="ja_JP.UTF-8"

Keep the default "/etc/default/locale" file for other programs as the the following.

LANG="en_US.UTF-8"

This is the most generic technique to customize locale and makes the menu selection dialog of gdm3(1) itself to be localized.

Alternatively for this case, you may simply change locale using the "~/.xsessionrc" file.

对于跨平台的数据交换(参见 第 10.1.7 节 “Removable storage device”),你需要使用特殊的编码挂载文件系统.举个例子，不使用选项时，mount(8) 假设 vfat 文件系统 使用 CP437. 你需要给文件名提供明确的挂载选项来使用UTF-8 或 CP932.

	注意
	在 GNOME 这类的现代桌面环境下，当自动挂载一个热拔插 U 盘时，你可以提供这样的挂载选项。右击桌面上的图标，点击 "Drive" , "Setting", 输入 "utf8" 到 "Mount options:". 当这个 U 盘下次挂载是，UTF-8 就可以了。

	注意
	如果你在升级一个系统，或者从老的非 UTF-8 系统迁移磁盘，非 ASCII 字符的文件名也许是使用老旧的 ISO-8859-1 或 eucJP 来编码. 请寻求文本转换工具把他们转换到 UTF-8. 参见 第 11.1 节 “Text data conversion tools”.

在默认情况下，Samba 对新的客户端(Windows NT, 200x, XP)使用 Unicode，但对老的客户端(DOS 和 Windows 9x/Me)使用 CP850.可以在 "/etc/samba/smb.conf" 文件里面，使用"dos charset" 来改变老客户端的这个默认编码。比如说，CP932 表示为日语。

在 Debian 系统中显示的许多文档和文本信息有翻译存在，比如错误信息、标准程序输出、菜单和手册页。GNU gettext(1) 命令工具链是大部分翻译活动的后端工具。

aptitude(8) 里，"Tasks" → "Localization" 提供一个有用的二进制包扩展列表， 给应用程序增加本地化信息和提供翻译文档。

举个例子，你可以安装 manpages-<LANG> 包来获得本地化 man 手册页信息。从 "/usr/share/man/it/" 来读取 <programname> 意大利语的 man 手册页 ,执行下面的操作。

LANG=it_IT.UTF-8 man <programname>

ls(1) 的日期格式受 locale 影响. "LANG=C ls -l" 和 "LANG=en_US.UTF-8" 的日期格式是不一样的(参见 第 9.2.5 节 “Customized display of time and date”).

不同 locales 的数字标点不一样.比如说，英语 locale, 一千点一显示为 "1,000.1"，而在德语 locale,它显示为 "1.000,1". 你可以在电子表格程序里面看到这个不同。