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LOCALE(7) Linux Programmer's Manual LOCALE(7)
locale - description of multilanguage support
#include <locale.h>
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 version 2.3 of the
GNU C library. 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.
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.
/usr/lib/locale/locale-archive
Usual default locale archive location.
/usr/lib/locale
Usual default path for compiled individual locale files.
POSIX.1-2001.
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)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2015-07-23 LOCALE(7)
Pages that refer to this page: locale(1), localectl(1), localedef(1), pg(1), systemd(1), catopen(3), duplocale(3), isalpha(3), localeconv(3), newlocale(3), nl_langinfo(3), setlocale(3), strerror(3), strfmon(3), toupper(3), towlower(3), towupper(3), uselocale(3), crontab(5), locale(5), locale.conf(5), environ(7), glob(7)