i18n_intro(5)i18n_intro(5)NAME
i18n_intro, i18n, LANG, LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES,
LC_MONETARY, LC_NUMERIC, LC_TIME - Introduction to internationalization
(I18N)
DESCRIPTION
Internationalization refers to the process of developing programs with‐
out prior knowledge of the language, cultural data, or character-encod‐
ing 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 with the operating system
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. How‐
ever, 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, charac‐
ter input methods, and other kinds of specialized software.
See the following reference pages for additional introductory informa‐
tion on topics related to internationalization: For more information on
localization and locales For an introduction to codeset conversion For
a summary of printer support for native languages
Characters, Character Sets, and Codesets
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 con‐
struct the words and other elementary units of a native language or
computer language. A character set specifies only 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 sup‐
port one or more character sets and establishes the one-to-one rela‐
tionship 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 (Setting Locale)
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. See the System
Administration manual for information about setting systemwide defaults
for shells. See setlocale(3) and Writing Software for the International
Market for information on how applications query or set locale require‐
ments 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:
language_territory.codeset[@modifier]
Where language represents the human language of the locale, territory
represents a geographic country or region, codeset is the coded charac‐
ter set used in the locale, and the optional @modifier suffix repre‐
sents additional information for localization of data.
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 Tra‐
ditional Chinese language, Hong Kong cultural data, and the DEC Hanyu
codeset: % setenv LANG zh_HK.dechanyu
Locale name formats can vary from vendor to vendor. Use the locale -a
command to display the names of locales installed on your system. See
l10n_intro(5) 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 vari‐
ables and what they control follow: String collation Character classi‐
fication 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
A locale can support only one set of date and time formats; how‐
ever, there can be several sets of date and time formats in use
for a particular language and territory. See l10n_intro(5) for
information about creating a site-specific version of a locale
to support date and time formats different from those supported
by an installed locale.
The operating system provides dense code locales and Unicode locales.
Unicode locales are installed in /usr/i18n/lib/nls/ucsloc/. Dense code
locales are installed in /usr/i18n/lib/nls/loc/. The Unicode locales
enable consistent wchar_t values across locales and platform interoper‐
ability. The system administrator, as root, can define the systemwide
default as Unicode locales or dense code locales by changing the sym‐
bolic link /usr/i18n/lib/nls/dloc/ from to l10n_intro(5) for a more
information on the Unicode locales and switching between Unicode and
dense code. See Unicode(5) for more information about UCS-4 and UTF-8
formats.
Unicode locales, with a UTF-8 suffix, use UTF-32 as the internal
process code and UTF-8 as the file format.
The operating system also includes a complete set of non-UTF-8 Unicode
locales in /usr/i18n/lib/nls/ucsloc/ that provide UTF-32 internal
process code for applications that require file code in the format of
the traditional UNIX or a proprietary codeset.
A @modifier suffix indicates locale variants that support alternative
rules for collation in Asian languages. Use locales with these suf‐
fixes only when setting LC_COLLATE. For example, three different sets
of collation rules (chuyin, radical, and stroke) 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_COL‐
LATE=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_MES‐
SAGES="zh_TW.eucTW" LC_ALL=
SEE ALSO
Commands: locale(1), setlocale(3)
Others: i18n_printing(5), iconv_intro(5), l10n_intro(5), Unicode(5)
Writing Software for the International Market
Using International Software
System Administration
i18n_intro(5)