i18n_intro, i18n, LANG, LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES, LC_MONETARY, LC_NUMERIC, LC_TIME - Introduction to internationalization (I18N)
Internationalization refers to the process of developing programs without prior knowledge of the language, cultural data, or character-encoding schemes that the programs are expected to handle. In other words, internationalization refers to the availability and use of interfaces that let programs modify their behavior at run time for operation in a specific language environment. The abbreviation I18N is often used to stand for internationalization as there are 18 characters between the beginning "I" and the ending "N" of that word.
The I18N interfaces and utilities provided in Tru64 UNIX conform to Issue 4 of X/Open CAE specifications.
A concept related to internationalization is localization (L10N), which refers to the process of establishing information within a computer system for each combination of native language, cultural data, and coded character set (codeset). A locale is a database that provides information for a unique combination of these three components. However, locales do not solve all of the problems that localization must address. Many native languages require additional support in the form of language-specific print filters, fonts, codeset converters, character input methods, and other kinds of specialized software.
For additional introductory information on topics related to internationalization,
refer to the following reference pages:
For more information on localization and locales
For an introduction to codeset conversion
For a summary of printer support for native languages
A character is a member of a set of elements used for the organization, control, or representation of data.
A character set is a set of alphabetic or other characters used to construct the words and other elementary units of a native language or computer language. A character set only specifies the characters that are included in the set. ASCII, CNS 11643 and DTSCS are examples of character sets.
A coded character set (codeset) is a set of unambiguous rules that support
one or more character sets and establishes the one-to-one relationship between
each character and its bit representation. In other words, a codeset consists
of the code points for characters in one or more character sets. For example,
DEC Hanyu (dechanyu) is a codeset for Chinese and contains
code points for characters in the ASCII, CNS 11643-1986 (plane 1 and plane
2), and DTSCS character sets.
Language announcement is the mechanism by which language, cultural data, and codeset requirements are set either for the system as a whole or by individual users. An application can also set these requirements, although it is more common for an internationalized application to use the setting in effect for the user who runs the program. Refer to the System Administration manual for information about setting systemwide defaults for shells. Refer to setlocale(3) and Writing Software for the International Market for information on how applications query or set locale requirements at run time.
Language announcement is performed by setting one or more reserved environment variables to the name of an installed locale. Each locale has associated with it collating sequences, character conversion tables, character classification tables, formats for different kinds of data, and message catalogs. If the same locale meets user requirements in all these categories, set only the LANG environment variable to the locale name. A locale name usually has the following format:
The following Korn shell example sets LANG to a locale supporting the English language, United States cultural data, and ISO8859-1 codeset: $ LANG=en_US.ISO8859-1
The following C shell example sets LANG to a locale supporting the Traditional Chinese language, Hong Kong cultural data, and the DEC Hanyu codeset: % setenv LANG zh_HK.dechanyu
Note that locale name formats can vary from vendor to vendor. Use the locale -a command to display the names of locales installed on your system. Refer to the l10n_intro(5) reference page for a list of the locales provided with the Tru64 UNIX product.
An alternative way to set locale requirements for all locale categories is to set the LC_ALL environment variable. The difference between the LANG and LC_ALL variables is that LC_ALL is a high-precedence variable that overrides all other locale variables, including LANG. The LANG variable, on the other hand, is a low-precedence variable. When used by itself, the LANG variable implicitly sets all locale categories to the specified locale just as LC_ALL does. However, the LANG variable can be used together with variables for specific locale categories to create a multilocale environment. The category-specific locale variables and what they control follow: String collation Character classification Translations for messages and valid strings for "yes" and "no" responses The currency symbol and the format of monetary values The format of numeric values The format of date and time values
Some locale names have one or more @modifier suffixes. A locale with the suffix @ucs4 is for use by applications that require internal process code to be in UCS-4 format. See Unicode(5) for more information about UCS-4. Other @modifier suffixes indicate locale variants that support alternative rules for collation in Asian languages. Use locales with these suffixes only when setting LC_COLLATE. For example, there are three different sets of collation rules (chuyin, radical, and stroke) that can be used with the locale supporting the Chinese language, Taiwanese cultural data, and the Taiwanese EUC codeset. If Korn shell users want to use this locale, they might make the following settings: $ LANG=zh_TW.eucTW $ LC_COLLATE=zh_TW.eucTW@stroke
The preceding example implicitly sets all locale category variables to zh_TW.eucTW, except for the LC_COLLATE variable, which is set to zh_TW.eucTW@stroke. The following locale command displays the variable settings after these assignments:
$ locale LANG=zh_TW.eucTW LC_COLLATE=zh_TW.eucTW@stroke LC_CTYPE="zh_TW.eucTW" LC_MONETARY="zh_TW.eucTW" LC_NUMERIC="zh_TW.eucTW" LC_TIME="zh_TW.eucTW" LC_MESSAGES="zh_TW.eucTW" LC_ALL=
Commands: locale(1), setlocale(3)
Others: i18n_printing(5), iconv_intro(5), l10n_intro(5), Unicode(5)
Writing Software for the International Market