.\"     $NetBSD: nls.7,v 1.15 2009/04/09 02:51:54 joerg Exp $
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.Dd February 21, 2007
.Dt NLS 7
.Os
.Sh NAME
.Nm NLS
.Nd Native Language Support Overview
.Sh DESCRIPTION
Native 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:
.Pp
.Bl -bullet -offset indent -compact
.It
Character classifications
.It
Character comparison rules
.It
Character collation order
.It
Numeric and monetary formatting
.It
Date and time formatting
.It
Message-text language
.It
Character sets
.El
.Pp
All information pertaining to cultural conventions and language is
obtained at program run time.
.Pp
.Dq Internationalization
(often abbreviated
.Dq 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.
.Dq Localization
(often abbreviated
.Dq 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
.Dq locale .
.Pp
.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.
.Pp
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 :
.Pp
.Bl -tag -compact -width LC_MONETARYXX
.It Ev LC_COLLATE
string-collation order information
.It Ev LC_CTYPE
character classification, case conversion, and other character attributes
.It Ev LC_MESSAGES
the format for affirmative and negative responses
.It Ev LC_MONETARY
rules and symbols for formatting monetary numeric information
.It Ev LC_NUMERIC
rules and symbols for formatting nonmonetary numeric information
.It Ev LC_TIME
rules and symbols for formatting time and date information
.El
.Pp
Localization of the system is achieved by setting appropriate values
in environment variables to identify which locale should be used.
The environment variables have the same names as their respective
locale categories.
Additionally, the
.Ev LANG ,
.Ev LC_ALL ,
and
.Ev NLSPATH
environment variables are used.
The
.Ev NLSPATH
environment variable specifies a colon-separated list of directory names
where the message catalog files of the NLS database are located.
The
.Ev LC_ALL
and
.Ev LANG
environment variables also determine the current locale.
.Pp
The values of these environment variables contains a string format as:
.Pp
.Bd -literal
	language[_territory][.codeset][@modifier]
.Ed
.Pp
Valid values for the language field come from the ISO639 standard which
defines two-character codes for many languages.
Some common language codes are:
.Pp
.Bl -column "PERSIAN (farsi)" "Sy Code" "OCEANIC/INDONESIAN"
.It Sy Language Name Ta Sy Code Ta Sy Language Family
.It ABKHAZIAN	AB	IBERO-CAUCASIAN
.It AFAN (OROMO)	OM	HAMITIC
.It AFAR	AA	HAMITIC
.It AFRIKAANS	AF	GERMANIC
.It ALBANIAN	SQ	INDO-EUROPEAN (OTHER)
.It AMHARIC	AM	SEMITIC
.It ARABIC	AR	SEMITIC
.It ARMENIAN	HY	INDO-EUROPEAN (OTHER)
.It ASSAMESE	AS	INDIAN
.It AYMARA	AY	AMERINDIAN
.It AZERBAIJANI	AZ	TURKIC/ALTAIC
.It BASHKIR	BA	TURKIC/ALTAIC
.It BASQUE	EU	BASQUE
.It BENGALI	BN	INDIAN
.It BHUTANI	DZ	ASIAN
.It BIHARI	BH	INDIAN
.It BISLAMA     Ta BI   Ta ""
.It BRETON	BR	CELTIC
.It BULGARIAN	BG	SLAVIC
.It BURMESE	MY	ASIAN
.It BYELORUSSIAN	BE	SLAVIC
.It CAMBODIAN	KM	ASIAN
.It CATALAN	CA	ROMANCE
.It CHINESE	ZH	ASIAN
.It CORSICAN	CO	ROMANCE
.It CROATIAN	HR	SLAVIC
.It CZECH	CS	SLAVIC
.It DANISH	DA	GERMANIC
.It DUTCH	NL	GERMANIC
.It ENGLISH	EN	GERMANIC
.It ESPERANTO	EO	INTERNATIONAL AUX.
.It ESTONIAN	ET	FINNO-UGRIC
.It FAROESE	FO	GERMANIC
.It FIJI	FJ	OCEANIC/INDONESIAN
.It FINNISH	FI	FINNO-UGRIC
.It FRENCH	FR	ROMANCE
.It FRISIAN	FY	GERMANIC
.It GALICIAN	GL	ROMANCE
.It GEORGIAN	KA	IBERO-CAUCASIAN
.It GERMAN	DE	GERMANIC
.It GREEK	EL	LATIN/GREEK
.It GREENLANDIC	KL	ESKIMO
.It GUARANI	GN	AMERINDIAN
.It GUJARATI	GU	INDIAN
.It HAUSA	HA	NEGRO-AFRICAN
.It HEBREW	HE	SEMITIC
.It HINDI	HI	INDIAN
.It HUNGARIAN	HU	FINNO-UGRIC
.It ICELANDIC	IS	GERMANIC
.It INDONESIAN	ID	OCEANIC/INDONESIAN
.It INTERLINGUA	IA	INTERNATIONAL AUX.
.It INTERLINGUE	IE	INTERNATIONAL AUX.
.It INUKTITUT   Ta IU   Ta ""
.It INUPIAK	IK	ESKIMO
.It IRISH	GA	CELTIC
.It ITALIAN	IT	ROMANCE
.It JAPANESE	JA	ASIAN
.It JAVANESE	JV	OCEANIC/INDONESIAN
.It KANNADA	KN	DRAVIDIAN
.It KASHMIRI	KS	INDIAN
.It KAZAKH	KK	TURKIC/ALTAIC
.It KINYARWANDA	RW	NEGRO-AFRICAN
.It KIRGHIZ	KY	TURKIC/ALTAIC
.It KURUNDI	RN	NEGRO-AFRICAN
.It KOREAN	KO	ASIAN
.It KURDISH	KU	IRANIAN
.It LAOTHIAN	LO	ASIAN
.It LATIN	LA	LATIN/GREEK
.It LATVIAN	LV	BALTIC
.It LINGALA	LN	NEGRO-AFRICAN
.It LITHUANIAN	LT	BALTIC
.It MACEDONIAN	MK	SLAVIC
.It MALAGASY	MG	OCEANIC/INDONESIAN
.It MALAY	MS	OCEANIC/INDONESIAN
.It MALAYALAM	ML	DRAVIDIAN
.It MALTESE	MT	SEMITIC
.It MAORI	MI	OCEANIC/INDONESIAN
.It MARATHI	MR	INDIAN
.It MOLDAVIAN	MO	ROMANCE
.It MONGOLIAN   Ta MN   Ta ""
.It NAURU       Ta NA   Ta ""
.It NEPALI	NE	INDIAN
.It NORWEGIAN	NO	GERMANIC
.It OCCITAN	OC	ROMANCE
.It ORIYA	OR	INDIAN
.It PASHTO	PS	IRANIAN
.It PERSIAN (farsi)	FA	IRANIAN
.It POLISH	PL	SLAVIC
.It PORTUGUESE	PT	ROMANCE
.It PUNJABI	PA	INDIAN
.It QUECHUA	QU	AMERINDIAN
.It RHAETO-ROMANCE	RM	ROMANCE
.It ROMANIAN	RO	ROMANCE
.It RUSSIAN	RU	SLAVIC
.It SAMOAN	SM	OCEANIC/INDONESIAN
.It SANGHO	SG	NEGRO-AFRICAN
.It SANSKRIT	SA	INDIAN
.It SCOTS GAELIC	GD	CELTIC
.It SERBIAN	SR	SLAVIC
.It SERBO-CROATIAN	SH	SLAVIC
.It SESOTHO	ST	NEGRO-AFRICAN
.It SETSWANA	TN	NEGRO-AFRICAN
.It SHONA	SN	NEGRO-AFRICAN
.It SINDHI	SD	INDIAN
.It SINGHALESE	SI	INDIAN
.It SISWATI	SS	NEGRO-AFRICAN
.It SLOVAK	SK	SLAVIC
.It SLOVENIAN	SL	SLAVIC
.It SOMALI	SO	HAMITIC
.It SPANISH	ES	ROMANCE
.It SUNDANESE	SU	OCEANIC/INDONESIAN
.It SWAHILI	SW	NEGRO-AFRICAN
.It SWEDISH	SV	GERMANIC
.It TAGALOG	TL	OCEANIC/INDONESIAN
.It TAJIK	TG	IRANIAN
.It TAMIL	TA	DRAVIDIAN
.It TATAR	TT	TURKIC/ALTAIC
.It TELUGU	TE	DRAVIDIAN
.It THAI	TH	ASIAN
.It TIBETAN	BO	ASIAN
.It TIGRINYA	TI	SEMITIC
.It TONGA	TO	OCEANIC/INDONESIAN
.It TSONGA	TS	NEGRO-AFRICAN
.It TURKISH	TR	TURKIC/ALTAIC
.It TURKMEN	TK	TURKIC/ALTAIC
.It TWI	TW	NEGRO-AFRICAN
.It UIGUR       Ta UG   Ta ""
.It UKRAINIAN	UK	SLAVIC
.It URDU	UR	INDIAN
.It UZBEK	UZ	TURKIC/ALTAIC
.It VIETNAMESE	VI	ASIAN
.It VOLAPUK	VO	INTERNATIONAL AUX.
.It WELSH	CY	CELTIC
.It WOLOF	WO	NEGRO-AFRICAN
.It XHOSA	XH	NEGRO-AFRICAN
.It YIDDISH	YI	GERMANIC
.It YORUBA	YO	NEGRO-AFRICAN
.It ZHUANG      Ta ZA   Ta ""
.It ZULU	ZU	NEGRO-AFRICAN
.El
.Pp
For example, the locale for the Danish language spoken in Denmark
using the ISO 8859-1 character 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.
.Pp
The environment variable settings are queried by their priority level
in the following manner:
.Pp
.Bl -bullet
.It
If the
.Ev LC_ALL
environment variable is set, all six categories use the locale it
specifies.
.It
If the
.Ev LC_ALL
environment variable is not set, each individual category uses the
locale specified by its corresponding environment variable.
.It
If the
.Ev LC_ALL
environment variable is not set, and a value for a particular
.Ev LC_*
environment variable is not set, the value of the
.Ev LANG
environment variable specifies the default locale for all categories.
Only the
.Ev LANG
environment variable should be set in /etc/profile, since it makes it
most easy for the user to override the system default using the individual
.Ev LC_*
variables.
.It
If the
.Ev LC_ALL
environment variable is not set, a value for a particular
.Ev LC_*
environment variable is not set, and the value of the
.Ev LANG
environment variable is not set, the locale for that specific
category defaults to the C locale.
The C or POSIX locale assumes the ASCII character set and defines
information for the six categories.
.El
.Ss Character 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.
It is the encoding values in a character set that provide
the interface between the system and its input and output devices.
.Pp
The following character sets are supported in
.Nx :
.Bl -tag -width ISO_8859_family
.It ASCII
The American Standard Code for Information Exchange (ASCII) standard
specifies 128 Roman characters and control codes, encoded in a 7-bit
character encoding scheme.
.It ISO 8859 family
Industry-standard character sets specified by the ISO/IEC 8859
standard.
The standard is divided into 15 numbered parts, with each
part specifying broad script similarities.
Examples include Western European, Central European, Arabic, Cyrillic,
Hebrew, Greek, and Turkish.
The character sets use an 8-bit character encoding scheme which is
compatible with the ASCII character set.
.It Unicode
The Unicode character set is the full set of known abstract characters of
all real-world scripts.  It can be used in environments where multiple
scripts must be processed simultaneously.
Unicode is compatible with ISO 8859-1 (Western European) and ASCII.
Many character encoding schemes are available for Unicode, including UTF-8,
UTF-16 and UTF-32.
These encoding schemes are multi-byte encodings.
The UTF-8 encoding scheme uses 8-bit, variable-width encodings which is
compatible with ASCII.
The UTF-16 encoding scheme uses 16-bit, variable-width encodings.
The UTF-32 encoding scheme using 32-bit, fixed-width encodings.
.El
.Ss Font Sets
A font set contains the glyphs to be displayed on the screen for a
corresponding character in a character set.
A display must support a suitable font to display a character set.
If suitable fonts are available to the X server, then X clients can
include support for different character sets.
.Xr xterm 1
includes support for Unicode with UTF-8 encoding.
.Xr xfd 1
is useful for displaying all the characters in an X font.
.Pp
The
.Nx
.Xr wscons 4
console provides support for loading fonts using the
.Xr wsfontload 8
utility.
Currently, only fonts for the ISO8859-1 family of character sets are
supported.
.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.
.Pp
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.
.Pp
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.
.Pp
.Nx
supports two message catalog interfaces: the X/Open
.Xr catgets 3
interface and the Uniforum
.Xr gettext 3
interface.
The
.Xr catgets 3
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 character sets.
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.
.Ss Support for Multi-byte Encodings
Some character sets with multi-byte encodings may be difficult to decode,
or may contain state (i.e., adjacent characters are dependent).
ISO C specifies a set of functions using 'wide characters' which can handle
multi-byte encodings properly.
The behaviour of these functions is affected
by the
.Ev LC_CTYPE
category of the current locale.
.Pp
A wide character is specified in ISO C
as being a fixed number of bits wide and is stateless.
There are two types for wide characters:
.Em wchar_t
and
.Em wint_t .
.Em wchar_t
is a type which can contain one wide character and operates like 'char'
type does for one character.
.Em wint_t
can contain one wide character or WEOF (wide EOF).
.Pp
There are functions that operate on
.Em wchar_t ,
and substitute for functions operating on 'char'.
See
.Xr wmemchr 3
and
.Xr towlower 3
for details.
There are some additional functions that operate on
.Em wchar_t .
See
.Xr wctype 3
and
.Xr wctrans 3
for details.
.Pp
Wide characters should be used for all I/O processing which may rely
on locale-specific strings.
The two primary issues requiring special use of wide characters are:
.Bl -bullet -offset indent
.It
All I/O is performed using multibyte characters.
Input data is converted into wide characters immediately after
reading and data for output is converted from wide characters to
multi-byte encoding immediately before writing.
Conversion is controlled by the
.Xr mbstowcs 3 ,
.Xr mbsrtowcs 3 ,
.Xr wcstombs 3 ,
.Xr wcsrtombs 3 ,
.Xr mblen 3 ,
.Xr mbrlen 3 ,
and
.Xr  mbsinit 3 .
.It
Wide characters are used directly for I/O, using
.Xr getwchar 3 ,
.Xr fgetwc 3 ,
.Xr getwc 3 ,
.Xr ungetwc 3 ,
.Xr fgetws 3 ,
.Xr putwchar 3 ,
.Xr fputwc 3 ,
.Xr putwc 3 ,
and
.Xr fputws 3 .
They are also used for formatted I/O functions for wide characters
such as
.Xr fwscanf 3 ,
.Xr wscanf 3 ,
.Xr swscanf 3 ,
.Xr fwprintf 3 ,
.Xr wprintf 3 ,
.Xr swprintf 3 ,
.Xr vfwprintf 3 ,
.Xr vwprintf 3 ,
and
.Xr vswprintf 3 ,
and wide character identifier of %lc, %C, %ls, %S for conventional
formatted I/O functions.
.El
.Sh SEE ALSO
.Xr gencat 1 ,
.Xr xfd 1 ,
.Xr xterm 1 ,
.Xr catgets 3 ,
.Xr gettext 3 ,
.Xr nl_langinfo 3 ,
.Xr setlocale 3 ,
.Xr wsfontload 8
.Sh BUGS
This man page is incomplete.