NAME

setlocale, localeconv — natural language formatting for C

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <locale.h>

char *
setlocale(int category, const char *locale);

struct lconv *
localeconv(void);

DESCRIPTION

The setlocale() function sets the C library's notion of natural language formatting style for particular sets of routines. Each such style is called a ‘locale’ and is invoked using an appropriate name passed as a C string. The localeconv() routine returns the current locale's parameters for formatting numbers.

The setlocale() function recognizes several categories of routines. These are the categories and the sets of routines they select:

LC_ALL: Set the entire locale generically.
LC_COLLATE: Set a locale for string collation routines. This controls alphabetic ordering in strcoll() and strxfrm().
LC_CTYPE: Set a locale for the ctype(3) functions. This controls recognition of upper and lower case, alphabetic or non-alphabetic characters, and so on.
LC_MESSAGES: Set a locale for message catalogs. This controls the selection of message catalogs by the catgets(3) and gettext(3) families of functions.
LC_MONETARY: Set a locale for formatting monetary values; this affects the localeconv() function.
LC_NUMERIC: Set a locale for formatting numbers. This controls the formatting of decimal points in input and output of floating point numbers in functions such as printf() and scanf(), as well as values returned by localeconv().
LC_TIME: Set a locale for formatting dates and times using the strftime() function.

Only three locales are defined by default, the empty string "" which denotes the native environment, and the "C" and "POSIX" locales, which denote the C language environment. A locale argument of NULL causes setlocale() to return the current locale. By default, C programs start in the "C" locale. The format of the locale string is described in nls(7).

The only function in the library that sets the locale is setlocale(); the locale is never changed as a side effect of some other routine.

Changing the setting of LC_MESSAGES has no effect on catalogs that have already been opened by catopen(3).

The localeconv() function returns a pointer to a structure which provides parameters for formatting numbers, especially currency values:

struct lconv {
	char	*decimal_point;
	char	*thousands_sep;
	char	*grouping;
	char	*int_curr_symbol;
	char	*currency_symbol;
	char	*mon_decimal_point;
	char	*mon_thousands_sep;
	char	*mon_grouping;
	char	*positive_sign;
	char	*negative_sign;
	char	int_frac_digits;
	char	frac_digits;
	char	p_cs_precedes;
	char	p_sep_by_space;
	char	n_cs_precedes;
	char	n_sep_by_space;
	char	p_sign_posn;
	char	n_sign_posn;
	char	int_p_cs_precedes;
	char	int_n_cs_precedes;
	char	int_p_sep_by_space;
	char	int_n_sep_by_space;
	char	int_p_sign_posn;
	char	int_n_sign_posn;
};

The individual fields have the following meanings:

decimal_point: The decimal point character, except for monetary values.
thousands_sep: The separator between groups of digits before the decimal point, except for monetary values.
grouping: The sizes of the groups of digits, except for monetary values. This is a pointer to a vector of integers, each of size char, representing group size from low order digit groups to high order (right to left). The list may be terminated with 0 or CHAR_MAX. If the list is terminated with 0, the last group size before the 0 is repeated to account for all the digits. If the list is terminated with CHAR_MAX, no more grouping is performed.
int_curr_symbol: The standardized (ISO 4217:1995) international currency symbol.
currency_symbol: The local currency symbol.
mon_decimal_point: The decimal point character for monetary values.
mon_thousands_sep: The separator for digit groups in monetary values.
mon_grouping: Like grouping but for monetary values.
positive_sign: The character used to denote nonnegative monetary values, usually the empty string.
negative_sign: The character used to denote negative monetary values, usually a minus sign.
int_frac_digits: The number of digits after the decimal point in an internationally formatted monetary value.
frac_digits: The number of digits after the decimal point in an locally formatted monetary value.
p_cs_precedes: 1 if the currency symbol precedes the monetary value for nonnegative values, 0 if it follows.
p_sep_by_space: 1 if a space is inserted between the currency symbol and the monetary value for nonnegative values, 0 otherwise.
n_cs_precedes: Like p_cs_precedes but for negative values.
n_sep_by_space: Like p_sep_by_space but for negative values.
p_sign_posn: The location of the positive_sign with respect to a nonnegative quantity and the currency_symbol.
n_sign_posn: Like p_sign_posn but for negative currency values.
int_p_cs_precedes: 1 if the currency symbol precedes the internationally formatted monetary value for nonnegative values, 0 if it follows.
int_n_cs_precedes: Like int_p_cs_precedes but for negative values.
int_p_sep_by_space: 1 if a space is inserted between the currency symbol and the internationally formatted monetary value for nonnegative values, 0 otherwise.
int_n_sep_by_space: Like int_p_sep_by_space but for negative values.
int_p_sign_posn: The location of the positive_sign with respect to a nonnegative quantity and the currency_symbol, for internationally formatted nonnegative monetary values.
int_n_sign_posn: Like int_p_sign_posn but for negative values.

The positional parameters in p_sign_posn, n_sign_posn, int_p_sign_posn and int_n_sign_posn are encoded as follows:

0: Parentheses around the entire string.
1: Before the string.
2: After the string.
3: Just before currency_symbol.
4: Just after currency_symbol.

Unless mentioned above, an empty string as a value for a field indicates a zero length result or a value that is not in the current locale. A CHAR_MAX result similarly denotes an unavailable value.

RETURN VALUES

The setlocale() function returns NULL and fails to change the locale if the given combination of category and locale makes no sense. The localeconv() function returns a pointer to a static object which may be altered by later calls to setlocale() or localeconv().

Currently, setlocale() returns NULL and fails to change the locale when LC_COLLATE is modified independently of other values.

EXAMPLES

The following code illustrates how a program can initialize the international environment for one language, while selectively modifying the program's locale such that regular expressions and string operations can be applied to text recorded in a different language:

	setlocale(LC_ALL, "de");
	setlocale(LC_NUMERIC, "C");

When a process is started, its current locale is set to the C or POSIX locale. An internationalized program that depends on locale data not defined in the C or POSIX locale must invoke the setlocale subroutine in the following manner before using any of the locale-specific information:

	setlocale(LC_ALL, "");

FILES

The use of multibyte locales requires shared libraries located in /usr/lib/i18n.

STANDARDS

The setlocale() and localeconv() functions conform to ANSI X3.159-1989 (“ANSI C89”) and ISO/IEC 9899:1990 (“ISO C90”).

The int_p_cs_precedes, int_n_cs_precedes, int_p_sep_by_space, int_n_sep_by_space, int_p_sign_posn and int_n_sign_posn members of struct lconv were introduced in ISO/IEC 9899:1999 (“ISO C99”).

HISTORY

The setlocale() and localeconv() functions first appeared in 4.4BSD.

BUGS

In spite of the gnarly currency support in localeconv(), the standards don't include any functions for generalized currency formatting.

LC_COLLATE is unimplemented (but does not make sense for many languages). Use of LC_MONETARY could lead to misleading results until we have a real time currency conversion function. LC_NUMERIC and LC_TIME are personal choices and should not be wrapped up with the other categories.

Multibyte locales aren't supported for static binaries.