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.Dd February 12, 2003 .Dt NLS 7 .Os .Sh NAME .Nm NLS .Nd Natural Language Support Overview .Sh DESCRIPTION National Language Support (NLS) provides commands for a single worldwide operating system base. An internationalized system has no built-in assumptions or dependencies on language-specific or cultural-specific conventions such as:
p l -bullet -indent -compact t Character classifications t Character comparison rules t Character collation order t Numeric and monetary formatting t Date and time formatting t Message-text language t Code sets .El
p All information pertaining to cultural conventions and language is obtained at program run time.
p "Internationalization" (often abbreviated "i18n") refers to the operation by which system software is developed to support multiple cultural-specific and language-specific conventions. This is a generalization process by which the system is untied from calling only English strings or other English-specific conventions. "Localization" (often abbreviated "l10n") refers to the operations by which the user environment is customized to handle its input and output appropriate for specific language and cultural conventions. This is a specialization process, by which generic methods already implemented in an internationalized system are used in specific ways. The formal description of cultural conventions for some country, together with all associated translations targeted to the native language, is called the "locale".
p .Nx provides extensive support to programmers and system developers to enable internationalized software to be developed. .Nx also supplies a large variety of locales for system localization. .Ss Localization of Information All locale information is accessible to programs at run time so that data is processed and displayed correctly for specific cultural conventions and language.
p A locale is divided into categories. A category is a group of language-specific and culture-specific conventions as outlined in the list above. ISO C specifies the following six standard categories supported by .Nx :
p l -tag -compact -width LC_MESSAGES t LC_COLLATE string-collation order information t LC_CTYPE character classification, case conversion, and other character attributes t LC_MESSAGES the format for affirmative and negative responses t LC_MONETARY rules and symbols for formatting monetary numeric information t LC_NUMERIC rules and symbols for formatting nonmonetary numeric information t LC_TIME rules and symbols for formatting time and date information .El
p Localization of the system is achieved by setting appropriate values in environment variables to identify which locale should be used. The following environment variables are used: LANG, LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES, LC_MONETARY, LC_NUMERIC, LC_TIME, and NLSPATH. The NLSPATH environment variable specifies a colon-separated list of directory names where the message catalog files of the NLS database are located. The LC_COLLATE, LC_CTYPE, LC_MONETARY, LC_NUMERIC, LC_TIME, and LC_MESSAGES environment variables determine the current values for their respective categories. The LC_ALL and LANG environment variables also determine the current locale.
p The values of these environment variables contains a string format as:
p d -literal language[_territory][.codeset][@modifier] .Ed
p For example, the locale for the Danish language spoken in Denmark using the ISO8859-1 code set is da_DK.ISO8859-1. The da stands for the Danish language and the DK stands for Denmark. The short form of da_DK is sufficient to indicate this locale.
p The environment variable settings are queried by their priority level in the following manner:
p l -bullet t If the LC_ALL environment variable is set, all six categories use the locale it specified. For example, if the LC_ALL environment variable is set to en_US and the LANG environment variable is set to fr_FR, each of the six categories is defined as the en_US locale. t If the LC_ALL environment variable is not set, each individual category uses the locale specified by its corresponding environment variable. For example, if the LC_ALL environment variable is not set, the LC_COLLATE environment variable is set to de_DE, and the LC_TIME environment variable is set to fr_CA, then the LC_COLLATE category is defined as de_DE and the LC_TIME category is defined as fr_CA. Neither environment variable has precedence over the other in this situation. t If the LC_ALL environment variable is not set, and a value for a particular LC_* environment variable is not set, the value of the LANG environment variable determines the definition for that specific category. For example, if the LC_ALL environment variable is not set, the LC_CTYPE environment variable is set to en_US, the LC_NUMERIC environment variable is not set, and the LANG environment variable is set to is_IS, then the LC_CTYPE category is defined as en_US and the LC_NUMERIC category to defined as is_IS. The LANG environment variable specifies the locale for only those categories not previously determined by an LC_* environment variable. t If the LC_ALL environment variable is not set, a value for a particular LC_* environment variable is not set, and the value of the LANG environment variable is not set, the locale for that specific category defaults to the C locale. The C or POSIX locale assumes the 7-bit ASCII character set and defines information for the six categories. For example, if the LC_ALL environment variable is not set, the LC_MONETARY environment variable is set to sv_SE, the LC_TIME environment variable is not set, and the LANG environment variable is not set, then the LC_MONETARY category is defined as sv_SE and the LC_TIME category as C. .El .Ss Code Sets A character is any symbol used for the organization, control, or representation of data. A group of such symbols used to describe a particular language make up a character set. A code set contains the encoding values (conversion from bits to displayed characters) for a character set. It is the encoding values in a code set that provide the interface between the system and its input and output devices.
p The following code sets are supported in .Nx l -tag -width ISO8859_family t ISO8859 family Industry-standard code sets are provided by means of the ISO8859 family of code sets, which provide a range of single-byte code set support that includes Latin-1, Latin-2, Arabic, Cyrillic, Hebrew, Greek, and Turkish. The eucJP code set is the industry-standard code set used to support the Japanese locale. t Unicode A Unicode environment based on the UTF-8 codeset is supported for all supported language/territories. UTF-8 provides character support for most of the major languages of the world and can be used in environments where multiple languages must be processed simultaneously. .El .Ss Internationalization for Programmers To facilitate translations of messages into various languages and to make the translated messages available to the program based on a user's locale, it is necessary to keep messages separate from the programs and provide them in the form of message catalogs that a program can access at run time.
p Access to locale information is provided through the .Xr setlocale 3 and .Xr nl_langinfo 3 interfaces. See their respective man pages for further information.
p Message source files containing application messages are created by the programmer and converted to message catalogs. These catalogs are used by the application to retrieve and display messages, as needed.
p .Nx supports two message catalog interfaces: the X/Open .Xr catgets 3 interface and the Uniforum .Xr gettext 3 interface. The .Xr catgets interface has the advantage that it belongs to a standard which is well supported. Unfortunately the interface is complicated to use and maintenance of the catalogs is difficult. The implementation also doesn't support different codesets. The .Xr gettext 3 interface has not been standardized yet, however it is being supported by an increasing number of systems. It also provides many additional tools which make programming and catalog maintenance much easier. .Sh SEE ALSO .Xr gencat 1 , .Xr catgets 3 , .Xr gettext 3 , .Xr nl_langinfo 3 , .Xr setlocale 3 .Sh BUGS This man page is incomplete.