NetBSD/share/man/man7/nls.7

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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
.nf
.ta \w'SERBO-CROATIAN'u+2n +\w'DE'u+5n +\w'OCEANIC/INDONESIAN'u+2nC
\fILanguage Name\fP	\fICode\fP	\fILanguage Family\fP
.ta \w'SERBO-CROATIAN'u+2n +\w'DE'u+5n +\w'OCEANIC/INDONESIAN'u+2nC
.sp 5p
ABKHAZIAN	AB	IBERO-CAUCASIAN
AFAN (OROMO)	OM	HAMITIC
AFAR	AA	HAMITIC
AFRIKAANS	AF	GERMANIC
ALBANIAN	SQ	INDO-EUROPEAN (OTHER)
AMHARIC	AM	SEMITIC
ARABIC	AR	SEMITIC
ARMENIAN	HY	INDO-EUROPEAN (OTHER)
ASSAMESE	AS	INDIAN
AYMARA	AY	AMERINDIAN
AZERBAIJANI	AZ	TURKIC/ALTAIC
BASHKIR	BA	TURKIC/ALTAIC
BASQUE	EU	BASQUE
BENGALI	BN	INDIAN
BHUTANI	DZ	ASIAN
BIHARI	BH	INDIAN
BISLAMA	BI
BRETON	BR	CELTIC
BULGARIAN	BG	SLAVIC
BURMESE	MY	ASIAN
BYELORUSSIAN	BE	SLAVIC
CAMBODIAN	KM	ASIAN
CATALAN	CA	ROMANCE
CHINESE	ZH	ASIAN
CORSICAN	CO	ROMANCE
CROATIAN	HR	SLAVIC
CZECH	CS	SLAVIC
DANISH	DA	GERMANIC
DUTCH	NL	GERMANIC
ENGLISH	EN	GERMANIC
ESPERANTO	EO	INTERNATIONAL AUX.
ESTONIAN	ET	FINNO-UGRIC
FAROESE	FO	GERMANIC
FIJI	FJ	OCEANIC/INDONESIAN
FINNISH	FI	FINNO-UGRIC
FRENCH	FR	ROMANCE
FRISIAN	FY	GERMANIC
GALICIAN	GL	ROMANCE
GEORGIAN	KA	IBERO-CAUCASIAN
GERMAN	DE	GERMANIC
GREEK	EL	LATIN/GREEK
GREENLANDIC	KL	ESKIMO
GUARANI	GN	AMERINDIAN
GUJARATI	GU	INDIAN
HAUSA	HA	NEGRO-AFRICAN
HEBREW	HE	SEMITIC
HINDI	HI	INDIAN
HUNGARIAN	HU	FINNO-UGRIC
ICELANDIC	IS	GERMANIC
INDONESIAN	ID	OCEANIC/INDONESIAN
INTERLINGUA	IA	INTERNATIONAL AUX.
INTERLINGUE	IE	INTERNATIONAL AUX.
INUKTITUT	IU
INUPIAK	IK	ESKIMO
IRISH	GA	CELTIC
ITALIAN	IT	ROMANCE
JAPANESE	JA	ASIAN
JAVANESE	JV	OCEANIC/INDONESIAN
KANNADA	KN	DRAVIDIAN
KASHMIRI	KS	INDIAN
KAZAKH	KK	TURKIC/ALTAIC
KINYARWANDA	RW	NEGRO-AFRICAN
KIRGHIZ	KY	TURKIC/ALTAIC
KURUNDI	RN	NEGRO-AFRICAN
KOREAN	KO	ASIAN
KURDISH	KU	IRANIAN
LAOTHIAN	LO	ASIAN
LATIN	LA	LATIN/GREEK
LATVIAN	LV	BALTIC
LINGALA	LN	NEGRO-AFRICAN
LITHUANIAN	LT	BALTIC
MACEDONIAN	MK	SLAVIC
MALAGASY	MG	OCEANIC/INDONESIAN
MALAY	MS	OCEANIC/INDONESIAN
MALAYALAM	ML	DRAVIDIAN
MALTESE	MT	SEMITIC
MAORI	MI	OCEANIC/INDONESIAN
MARATHI	MR	INDIAN
MOLDAVIAN	MO	ROMANCE
MONGOLIAN	MN
NAURU	NA
NEPALI	NE	INDIAN
NORWEGIAN	NO	GERMANIC
OCCITAN	OC	ROMANCE
ORIYA	OR	INDIAN
PASHTO	PS	IRANIAN
PERSIAN (farsi)	FA	IRANIAN
POLISH	PL	SLAVIC
PORTUGUESE	PT	ROMANCE
PUNJABI	PA	INDIAN
QUECHUA	QU	AMERINDIAN
RHAETO-ROMANCE  RM	ROMANCE
ROMANIAN	RO	ROMANCE
RUSSIAN	RU	SLAVIC
SAMOAN	SM	OCEANIC/INDONESIAN
SANGHO	SG	NEGRO-AFRICAN
SANSKRIT	SA	INDIAN
SCOTS GAELIC	GD	CELTIC
SERBIAN	SR	SLAVIC
SERBO-CROATIAN  SH	SLAVIC
SESOTHO	ST	NEGRO-AFRICAN
SETSWANA	TN	NEGRO-AFRICAN
SHONA	SN	NEGRO-AFRICAN
SINDHI	SD	INDIAN
SINGHALESE	SI	INDIAN
SISWATI	SS	NEGRO-AFRICAN
SLOVAK	SK	SLAVIC
SLOVENIAN	SL	SLAVIC
SOMALI	SO	HAMITIC
SPANISH	ES	ROMANCE
SUNDANESE	SU	OCEANIC/INDONESIAN
SWAHILI	SW	NEGRO-AFRICAN
SWEDISH	SV	GERMANIC
TAGALOG	TL	OCEANIC/INDONESIAN
TAJIK	TG	IRANIAN
TAMIL	TA	DRAVIDIAN
TATAR	TT	TURKIC/ALTAIC
TELUGU	TE	DRAVIDIAN
THAI	TH	ASIAN
TIBETAN	BO	ASIAN
TIGRINYA	TI	SEMITIC
TONGA	TO	OCEANIC/INDONESIAN
TSONGA	TS	NEGRO-AFRICAN
TURKISH	TR	TURKIC/ALTAIC
TURKMEN	TK	TURKIC/ALTAIC
TWI	TW	NEGRO-AFRICAN
UIGUR	UG
UKRAINIAN	UK	SLAVIC
URDU	UR	INDIAN
UZBEK	UZ	TURKIC/ALTAIC
VIETNAMESE	VI	ASIAN
VOLAPUK	VO	INTERNATIONAL AUX.
WELSH	CY	CELTIC
WOLOF	WO	NEGRO-AFRICAN
XHOSA	XH	NEGRO-AFRICAN
YIDDISH	YI	GERMANIC
YORUBA	YO	NEGRO-AFRICAN
ZHUANG	ZA
ZULU	ZU	NEGRO-AFRICAN
.ta
.fi
.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.