26. Localization <locale.h>

The header <locale.h> declares two functions, one type, and defines several macros.

The type is

struct lconv

which contains members related to the formatting of numeric values. The structure shall contain at least the following members, in any order. The semantics of the members and their normal ranges are explained in The localeconv function. In the “C” locale, the members shall have the values specified in the comments.

char *decimal_point;     // "."
char *thousands_sep;     // ""
char *grouping;          // ""
char *mon_decimal_point; // ""
char *mon_thousands_sep; // ""
char *mon_grouping;      // ""
char *positive_sign;     // ""
char *negative_sign;     // ""
char *currency_symbol;   // ""
char frac_digits;        // CHAR_MAX
char p_cs_precedes;      // CHAR_MAX
char n_cs_precedes;      // CHAR_MAX
char p_sep_by_space;     // CHAR_MAX
char n_sep_by_space;     // CHAR_MAX
char p_sign_posn;        // CHAR_MAX
char n_sign_posn;        // CHAR_MAX
char *int_curr_symbol;   // ""
char int_frac_digits;    // CHAR_MAX
char int_p_cs_precedes;  // CHAR_MAX
char int_n_cs_precedes;  // CHAR_MAX
char int_p_sep_by_space; // CHAR_MAX
char int_n_sep_by_space; // CHAR_MAX
char int_p_sign_posn;    // CHAR_MAX
char int_n_sign_posn;    // CHAR_MAX

The macros defined are NULL (described in Common definitions <stddef.h>); and

LC_ALL
LC_COLLATE
LC_CTYPE
LC_MONETARY
LC_NUMERIC
LC_TIME

which expand to integer constant expressions with distinct values, suitable for use as the first argument to the setlocale function. [1] Additional macro definitions, beginning with the characters LC_ and an uppercase letter,

[1]ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.

26.1. Locale control

26.1.1. The setlocale function

Synopsis

#include <locale.h>
char *setlocale(int category, const char *locale);

Description

The setlocale function selects the appropriate portion of the program’s locale as specified by the category and locale arguments. The setlocale function may be used to change or query the program’s entire current locale or portions thereof. The value LC_ALL for category names the program’s entire locale; the other values for category name only a portion of the program’s locale. LC_COLLATE affects the behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of the character handling functions [2] and the multibyte and wide character functions. LC_MONETARY affects the monetary formatting information returned by the localeconv function. LC_NUMERIC affects the decimal-point character for the formatted input/output functions and the string conversion functions, as well as the nonmonetary formatting information returned by the localeconv function. LC_TIME affects the behavior of the strftime and wcsftime functions.

A value of “C” for locale specifies the minimal environment for C translation; a value of “” for locale specifies the locale-specific native environment. Other implementation-defined strings may be passed as the second argument to setlocale.

[2]The only functions in Character Handling <ctype.h> whose behavior is not affected by the current locale are isdigit and isxdigit.

At program startup, the equivalent of

setlocale(LC_ALL, "C");

is executed.

The implementation shall behave as if no library function calls the setlocale function.

Returns

If a pointer to a string is given for locale and the selection can be honored, the setlocale function returns a pointer to the string associated with the specified category for the new locale. If the selection cannot be honored, the setlocale function returns a null pointer and the program’s locale is not changed.

A null pointer for locale causes the setlocale function to return a pointer to the string associated with the category for the program’s current locale; the program’s locale is not changed. [3]

The pointer to string returned by the setlocale function is such that a subsequent call with that string value and its associated category will restore that part of the program’s locale. The string pointed to shall not be modified by the program, but may be overwritten by a subsequent call to the setlocale function.

Forward references: formatted input/output functions (Formatted input/output functions), multibyte/wide character conversion functions (Multibyte/wide character conversion functions), multibyte/wide string conversion functions (Multibyte/wide string conversion functions), numeric conversion functions (Numeric conversion functions), the strcoll function (The strcoll function), the strftime function (The strftime function), the strxfrm function (The strxfrm function).

[3]The implementation shall arrange to encode in a string the various categories due to a heterogeneous locale when category has the value LC_ALL.

26.2. Numeric formatting convention inquiry

26.2.1. The localeconv function

Synopsis

#include <locale.h>
struct lconv *localeconv(void);

Description

The localeconv function sets the components of an object with type struct lconv with values appropriate for the formatting of numeric quantities (monetary and otherwise) according to the rules of the current locale.

The members of the structure with type char * are pointers to strings, any of which (except decimal_point) can point to “”, to indicate that the value is not available in the current locale or is of zero length. Apart from grouping and mon_grouping, the strings shall start and end in the initial shift state. The members with type char are nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not available in the current locale. The members include the following:

char *decimal_point

The decimal-point character used to format nonmonetary quantities.

char *thousands_sep

The character used to separate groups of digits before the decimal-point. character in formatted nonmonetary quantities.

char *grouping

A string whose elements indicate the size of each group of digits in formatted nonmonetary quantities.

char *mon_decimal_point

The decimal-point used to format monetary quantities.

char *mon_thousands_sep

The separator for groups of digits before the decimal-point in formatted monetary quantities.

char *mon_grouping

A string whose elements indicate the size of each group of digits in formatted monetary quantities.

char *positive_sign

The string used to indicate a nonnegative-valued formatted monetary quantity.

char *negative_sign

The string used to indicate a negative-valued formatted monetary quantity.

char *currency_symbol

The local currency symbol applicable to the current locale.

char frac_digits

The number of fractional digits (those after the decimal-point) to be displayed in a locally formatted monetary quantity.

char p_cs_precedes

Set to 1 or 0 if the currency_symbol respectively precedes or succeeds the value for a nonnegative locally formatted monetary quantity.

char n_cs_precedes

Set to 1 or 0 if the currency_symbol respectively precedes or succeeds the value for a negative locally formatted monetary quantity.

char p_sep_by_space

Set to a value indicating the separation of the currency_symbol, the sign string, and the value for a nonnegative locally formatted monetary quantity.

char n_sep_by_space

Set to a value indicating the separation of the currency_symbol, the sign string, and the value for a negative locally formatted monetary quantity.

char p_sign_posn

Set to a value indicating the positioning of the positive_sign for a nonnegative locally formatted monetary quantity.

char n_sign_posn

Set to a value indicating the positioning of the negative_sign for a negative locally formatted monetary quantity.

char *int_curr_symbol

The international currency symbol applicable to the current locale. The first three characters contain the alphabetic international currency symbol in accordance with those specified in ISO 4217. The fourth character (immediately preceding the null character) is the character used to separate the international currency symbol from the monetary quantity.

char int_frac_digits

The number of fractional digits (those after the decimal-point) to be displayed in an internationally formatted monetary quantity.

char int_p_cs_precedes

Set to 1 or 0 if the int_curr_symbol respectively precedes or succeeds the value for a nonnegative internationally formatted monetary quantity.

char int_n_cs_precedes

Set to 1 or 0 if the int_curr_symbol respectively precedes or succeeds the value for a negative internationally formatted monetary quantity.

char int_p_sep_by_space

Set to a value indicating the separation of the int_curr_symbol, the sign string, and the value for a nonnegative internationally formatted monetary quantity.

char int_n_sep_by_space

Set to a value indicating the separation of the int_curr_symbol, the sign string, and the value for a negative internationally formatted monetary quantity.

char int_p_sign_posn

Set to a value indicating the positioning of the positive_sign for a nonnegative internationally formatted monetary quantity.

char int_n_sign_posn

Set to a value indicating the positioning of the negative_sign for a negative internationally formatted monetary quantity.

The elements of grouping and mon_grouping are interpreted according to the following:

CHAR_MAX No further grouping is to be performed.
0 The previous element is to be repeatedly used for the remainder of the
digits.
other The integer value is the number of digits that compose the current group.
The next element is examined to determine the size of the next group of
digits before the current group.

The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space and int_n_sep_by_space are interpreted according to the following:

0 No space separates the currency symbol and value.
1 If the currency symbol and sign string are adjacent, a space separates them from the
value; otherwise, a space separates the currency symbol from the value.
2 If the currency symbol and sign string are adjacent, a space separates them;
otherwise, a space separates the sign string from the value.

For int_p_sep_by_space and int_n_sep_by_space, the fourth character of int_curr_symbol is used instead of a space.

The values of p_sign_posn, n_sign_posn, int_p_sign_posn and int_n_sign_posn are interpreted according to the following:

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.

The implementation shall behave as if no library function calls the localeconv function.

Returns

The localeconv function returns a pointer to the filled-in object. The structure pointed to by the return value shall not be modified by the program, but may be overwritten by a subsequent call to the localeconv function. In addition, calls to the setlocale function with categories LC_ALL, LC_MONETARY or LC_NUMERIC may overwrite the contents of the structure.

  Local format International format
Country Positive Negative Postive Negative
Country1 1.234,56 mk -1.234,56 mk FIM 1.234,56 FIM -1.234,56
Country2 L.1.234 -L.1.234 ITL 1.234 -ITL 1.234
Country3 f 1.234,56 f -1.234,56 NLG 1.234,56 NLG -1.234,56
Country4 SFrs.1,234.56 SFrs.1,234.56C CHF 1,234.56 CHF 1,234.56C

For these four countries, the respective values for the monetary members of the structure returned by localeconv could be:

  Country1 Country2 Country3 Country4
mon_decimal_point “,” “” “,” “.”
mon_thousands_sep “.” “.” “.” “,”
mon_grouping “\3” “\3” “\3” “\3”
positive_sign “” “” “” “”
negative_sign “-“ “-“ “-“ “C”
currency_symbol “mk” “L.” “\u0192” “SFrs.”
frac_digits 2 0 2 2
p_cs_precedesd 0 1 1 1
n_cs_precedes 0 1 1 1
p_sep_by_space 1 0 1 0
n_sep_by_space 1 0 2 0
p_sign_posn 1 1 1 1
n_sign_posn 1 1 4 2
int_curr_symbol “FIM “ “ITL “ “NLG “ “CHF “
int_frac_digits 2 0 2 2
int_p_cs_precedes 1 1 1 1
int_n_cs_precedes 1 1 1 1
int_p_sep_by_space 1 1 1 1
int_n_sep_by_space 2 1 2 1
int_p_sign_posn 1 1 1 1
int_n_sign_posn 4 1 4 2

EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space and sign_posn members affect the formatted value.

p_cs_precedes p_sign_posn p_sep_by_space
    0 1 2
0 0 (1.25$) (1.25 $) (1.25$)
0 1 +1.25$ +1.25 $ + 1.25$
0 2 1.25$+ 1.25 $+ 1.25$ +
0 3 1.25+$ 1.25 +$ 1.25+ $
0 4 1.25$+ 1.25 $+ 1.25$ +
1 0 ($1.25) ($ 1.25) ($1.25)
1 1 +$1.25 +$ 1.25 + $1.25
1 2 $1.25+ $ 1.25+ $1.25 +
1 3 +$1.25 +$ 1.25 + $1.25
1 4 $+1.25 $+ 1.25 $ +1.25