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NAME
locale - description of multilanguage support
SYNOPSIS
#include <locale.h>
DESCRIPTION
A locale is a set of language and cultural rules. These cover aspects such as language for messages,
different character sets, lexicographic conventions, and so on. A program needs to be able to determine
its locale and act accordingly to be portable to different cultures.
The header <locale.h> declares data types, functions, and macros which are useful in this task.
The functions it declares are setlocale(3) to set the current locale, and localeconv(3) to get
information about number formatting.
There are different categories for locale information a program might need; they are declared as macros.
Using them as the first argument to the setlocale(3) function, it is possible to set one of these to the
desired locale:
LC_ADDRESS (GNU extension, since glibc 2.2)
Change settings that describe the formats (e.g., postal addresses) used to describe locations and
geography-related items. Applications that need this information can use nl_langinfo(3) to
retrieve nonstandard elements, such as _NL_ADDRESS_COUNTRY_NAME (country name, in the language of
the locale) and _NL_ADDRESS_LANG_NAME (language name, in the language of the locale), which return
strings such as "Deutschland" and "Deutsch" (for German-language locales). (Other element names
are listed in <langinfo.h>.)
LC_COLLATE
This category governs the collation rules used for sorting and regular expressions, including
character equivalence classes and multicharacter collating elements. This locale category changes
the behavior of the functions strcoll(3) and strxfrm(3), which are used to compare strings in the
local alphabet. For example, the German sharp s is sorted as "ss".
LC_CTYPE
This category determines the interpretation of byte sequences as characters (e.g., single versus
multibyte characters), character classifications (e.g., alphabetic or digit), and the behavior of
character classes. On glibc systems, this category also determines the character transliteration
rules for iconv(1) and iconv(3). It changes the behavior of the character handling and
classification functions, such as isupper(3) and toupper(3), and the multibyte character functions
such as mblen(3) or wctomb(3).
LC_IDENTIFICATION (GNU extension, since glibc 2.2)
Change settings that relate to the metadata for the locale. Applications that need this
information can use nl_langinfo(3) to retrieve nonstandard elements, such as
_NL_IDENTIFICATION_TITLE (title of this locale document) and _NL_IDENTIFICATION_TERRITORY
(geographical territory to which this locale document applies), which might return strings such as
"English locale for the USA" and "USA". (Other element names are listed in <langinfo.h>.)
LC_MONETARY
This category determines the formatting used for monetary-related numeric values. This changes
the information returned by localeconv(3), which describes the way numbers are usually printed,
with details such as decimal point versus decimal comma. This information is internally used by
the function strfmon(3).
LC_MESSAGES
This category affects the language in which messages are displayed and what an affirmative or
negative answer looks like. The GNU C library contains the gettext(3), ngettext(3), and
rpmatch(3) functions to ease the use of this information. The GNU gettext family of functions
also obey the environment variable LANGUAGE (containing a colon-separated list of locales) if the
category is set to a valid locale other than "C". This category also affects the behavior of
catopen(3).
LC_MEASUREMENT (GNU extension, since glibc 2.2)
Change the settings relating to the measurement system in the locale (i.e., metric versus US
customary units). Applications can use nl_langinfo(3) to retrieve the nonstandard
_NL_MEASUREMENT_MEASUREMENT element, which returns a pointer to a character that has the value 1
(metric) or 2 (US customary units).
LC_NAME (GNU extension, since glibc 2.2)
Change settings that describe the formats used to address persons. Applications that need this
information can use nl_langinfo(3) to retrieve nonstandard elements, such as _NL_NAME_NAME_MR
(general salutation for men) and _NL_NAME_NAME_MS (general salutation for women) elements, which
return strings such as "Herr" and "Frau" (for German-language locales). (Other element names are
listed in <langinfo.h>.)
LC_NUMERIC
This category determines the formatting rules used for nonmonetary numeric values—for example, the
thousands separator and the radix character (a period in most English-speaking countries, but a
comma in many other regions). It affects functions such as printf(3), scanf(3), and strtod(3).
This information can also be read with the localeconv(3) function.
LC_PAPER (GNU extension, since glibc 2.2)
Change the settings relating to the dimensions of the standard paper size (e.g., US letter versus
A4). Applications that need the dimensions can obtain them by using nl_langinfo(3) to retrieve
the nonstandard _NL_PAPER_WIDTH and _NL_PAPER_HEIGHT elements, which return int values specifying
the dimensions in millimeters.
LC_TELEPHONE (GNU extension, since glibc 2.2)
Change settings that describe the formats to be used with telephone services. Applications that
need this information can use nl_langinfo(3) to retrieve nonstandard elements, such as
_NL_TELEPHONE_INT_PREFIX (international prefix used to call numbers in this locale), which returns
a string such as "49" (for Germany). (Other element names are listed in <langinfo.h>.)
LC_TIME
This category governs the formatting used for date and time values. For example, most of Europe
uses a 24-hour clock versus the 12-hour clock used in the United States. The setting of this
category affects the behavior of functions such as strftime(3) and strptime(3).
LC_ALL All of the above.
If the second argument to setlocale(3) is an empty string, "", for the default locale, it is determined
using the following steps:
(1) If there is a non-null environment variable LC_ALL, the value of LC_ALL is used.
(2) If an environment variable with the same name as one of the categories above exists and is non-null,
its value is used for that category.
(3) If there is a non-null environment variable LANG, the value of LANG is used.
Values about local numeric formatting is made available in a struct lconv returned by the localeconv(3)
function, which has the following declaration:
struct lconv {
/* Numeric (nonmonetary) information */
char *decimal_point; /* Radix character */
char *thousands_sep; /* Separator for digit groups to left
of radix character */
char *grouping; /* Each element is the number of digits in
a group; elements with higher indices
are further left. An element with value
CHAR_MAX means that no further grouping
is done. An element with value 0 means
that the previous element is used for
all groups further left. */
/* Remaining fields are for monetary information */
char *int_curr_symbol; /* First three chars are a currency
symbol from ISO 4217. Fourth char
is the separator. Fifth char
is '\0'. */
char *currency_symbol; /* Local currency symbol */
char *mon_decimal_point; /* Radix character */
char *mon_thousands_sep; /* Like thousands_sep above */
char *mon_grouping; /* Like grouping above */
char *positive_sign; /* Sign for positive values */
char *negative_sign; /* Sign for negative values */
char int_frac_digits; /* International fractional digits */
char frac_digits; /* Local fractional digits */
char p_cs_precedes; /* 1 if currency_symbol precedes a
positive value, 0 if succeeds */
char p_sep_by_space; /* 1 if a space separates
currency_symbol from a positive
value */
char n_cs_precedes; /* 1 if currency_symbol precedes a
negative value, 0 if succeeds */
char n_sep_by_space; /* 1 if a space separates
currency_symbol from a negative
value */
/* Positive and negative sign positions:
0 Parentheses surround the quantity and currency_symbol.
1 The sign string precedes the quantity and currency_symbol.
2 The sign string succeeds the quantity and currency_symbol.
3 The sign string immediately precedes the currency_symbol.
4 The sign string immediately succeeds the currency_symbol. */
char p_sign_posn;
char n_sign_posn;
};
POSIX.1-2008 extensions to the locale API
POSIX.1-2008 standardized a number of extensions to the locale API, based on implementations that first
appeared in glibc 2.3. These extensions are designed to address the problem that the traditional locale
APIs do not mix well with multithreaded applications and with applications that must deal with multiple
locales.
The extensions take the form of new functions for creating and manipulating locale objects (newlocale(3),
freelocale(3), duplocale(3), and uselocale(3)) and various new library functions with the suffix "_l"
(e.g., toupper_l(3)) that extend the traditional locale-dependent APIs (e.g., toupper(3)) to allow the
specification of a locale object that should apply when executing the function.
ENVIRONMENT
The following environment variable is used by newlocale(3) and setlocale(3), and thus affects all
unprivileged localized programs:
LOCPATH
A list of pathnames, separated by colons (':'), that should be used to find locale data. If this
variable is set, only the individual compiled locale data files from LOCPATH and the system
default locale data path are used; any available locale archives are not used (see localedef(1)).
The individual compiled locale data files are searched for under subdirectories which depend on
the currently used locale. For example, when en_GB.UTF-8 is used for a category, the following
subdirectories are searched for, in this order: en_GB.UTF-8, en_GB.utf8, en_GB, en.UTF-8, en.utf8,
and en.
FILES
/usr/lib/locale/locale-archive
Usual default locale archive location.
/usr/lib/locale
Usual default path for compiled individual locale files.
STANDARDS
POSIX.1-2001.
SEE ALSO
iconv(1), locale(1), localedef(1), catopen(3), gettext(3), iconv(3), localeconv(3), mbstowcs(3),
newlocale(3), ngettext(3), nl_langinfo(3), rpmatch(3), setlocale(3), strcoll(3), strfmon(3), strftime(3),
strxfrm(3), uselocale(3), wcstombs(3), locale(5), charsets(7), unicode(7), utf-8(7)
Linux man-pages 6.9.1 2024-06-15 locale(7)