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SETLOCALE(3) Library Functions Manual SETLOCALE(3)

setlocale, localeconvnatural language formatting for C

#include <locale.h>

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

struct lconv *

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

Set the entire locale generically.
Set a locale for string collation routines. This controls alphabetic ordering in strcoll(3) and strxfrm(3).
Set a locale for the functions declared in <ctype.h> and <wctype.h>. This controls recognition of upper and lower case, alphabetic or non-alphabetic characters, and so on.
Set a locale for message strings. Controls the behaviour of catopen(3) and internationalization tools.
Set a locale for formatting monetary values; this affects the localeconv() function.
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(3) and scanf(3), as well as values returned by localeconv().
Set a locale for formatting dates and times using the strftime(3) 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 () to return the current locale. By default, C programs start in the "C" locale. 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.

The () 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_p_sep_by_space;
	char	int_n_cs_precedes;
	char	int_n_sep_by_space;
	char	int_p_sign_posn;
	char	int_n_sign_posn;

The individual fields have the following meanings:

The decimal point character, except for currency values.
The separator between groups of digits before the decimal point, except for currency values.
The sizes of the groups of digits, except for currency 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.
The standardized international currency symbol.
The local currency symbol.
The decimal point character for currency values.
The separator for digit groups in currency values.
Like grouping but for currency values.
The character used to denote non-negative currency values, usually the empty string.
The character used to denote negative currency values, usually a minus sign.
The number of digits after the decimal point in an international-style currency value.
The number of digits after the decimal point in the local style for currency values.
1 if the currency symbol precedes the currency value for non-negative values, 0 if it follows.
1 if a space is inserted between the currency symbol and the currency value for non-negative values, 0 otherwise.
Like p_cs_precedes but for negative values.
Like p_sep_by_space but for negative values.
The location of the positive_sign with respect to a non-negative quantity and the currency_symbol, coded as follows:

Parentheses around the entire string.
Before the string.
After the string.
Just before currency_symbol.
Just after currency_symbol.
Like p_sign_posn but for negative currency values.
Like p_cs_precedes but for the international symbol.
Like n_cs_precedes but for the international symbol.
Like p_sep_by_space but for the international symbol.
Like n_sep_by_space but for the international symbol.
Like p_sign_posn but for the international symbol.
Like n_sign_posn but for the international 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.

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().

mklocale(1), catopen(3), printf(3), scanf(3), strcoll(3), strftime(3), strxfrm(3)

The setlocale() and localeconv() functions conform to ANSI X3.159-1989 (“ANSI C89”).

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

The current implementation supports only the "C" and "POSIX" locales for all but the LC_CTYPE locale.

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

LC_COLLATE 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.

September 21, 2015 OpenBSD-6.1