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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 local 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_COLLATE
This is used to change 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 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_MONETARY
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
changes the language messages are displayed in 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 these 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".
LC_NUMERIC
changes the information used by the printf(3) and scanf(3) family of functions, when they are
advised to use the locale-settings. This information can also be read with the localeconv(3)
function.
LC_TIME
changes the behavior of the strftime(3) function to display the current time in a locally
acceptable form; for example, most of Europe uses a 24-hour clock versus the 12-hour clock used in
the United States.
LC_ALL All of the above.
If the second argument to setlocale(3) is 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;
};
CONFORMING TO
POSIX.1-2001.
The GNU gettext functions are specified in LI18NUX2000.
SEE ALSO
locale(1), localedef(1), gettext(3), localeconv(3), ngettext(3), nl_langinfo(3), rpmatch(3),
setlocale(3), strcoll(3), strfmon(3), strftime(3), strxfrm(3)
COLOPHON
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