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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)