locale(7) Miscellaneous Information Manual locale(7)
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 ad-
dresses) 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_COUN-
TRY_NAME (country name, in the language of the locale) and
_NL_ADDRESS_LANG_NAME (language name, in the language of the lo-
cale), 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 deter-
mines 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. Ap-
plications 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-re-
lated 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 dis-
played and what an affirmative or negative answer looks like.
The GNU C library contains the gettext(3), ngettext(3), and rp-
match(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_MEASURE-
MENT_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 per-
sons. Applications that need this information can use nl_lang-
info(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 nonmone-
tary 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 re-
trieve the nonstandard _NL_PAPER_WIDTH and _NL_PAPER_HEIGHT ele-
ments, which return int values specifying the dimensions in mil-
limeters.
LC_TELEPHONE (GNU extension, since glibc 2.2)
Change settings that describe the formats to be used with tele-
phone 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 num-
bers 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 val-
ues. 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 strf-
time(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 cate-
gories 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 ex-
tensions are designed to address the problem that the traditional lo-
cale APIs do not mix well with multithreaded applications and with ap-
plications that must deal with multiple locales.
The extensions take the form of new functions for creating and manipu-
lating 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 setlo-
cale(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 in-
dividual 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), uni-
code(7), utf-8(7)
Linux man-pages 6.7 2024-02-25 locale(7)
Generated by dwww version 1.16 on Tue Dec 16 06:40:52 CET 2025.