< c‎ | locale
Defined in header <locale.h>
#define LC_ALL      /*implementation defined*/
#define LC_COLLATE  /*implementation defined*/
#define LC_CTYPE    /*implementation defined*/
#define LC_MONETARY /*implementation defined*/
#define LC_NUMERIC  /*implementation defined*/
#define LC_TIME     /*implementation defined*/

Each of the above macro constants expand to integer constant expressions with distinct values that are suitable for use as the first argument of setlocale.

Constant Explanation
LC_ALL selects the entire C locale
LC_COLLATE selects the collation category of the C locale
LC_CTYPE selects the character classification category of the C locale
LC_MONETARY selects the monetary formatting category of the C locale
LC_NUMERIC selects the numeric formatting category of the C locale
LC_TIME selects the time formatting category of the C locale

Additional macro constants, with names that begin with LC_ followed by at least one uppercase letter, may be defined in locale.h. For example, the POSIX specification requires LC_MESSAGES and the GNU C library additionally defines LC_PAPER, LC_NAME, LC_ADDRESS, LC_TELEPHONE, LC_MEASUREMENT, and LC_IDENTIFICATION.

[edit] Example

#include <stdio.h>
#include <locale.h>
#include <time.h>
#include <wchar.h>
int main()
    setlocale(LC_ALL, "en_US.UTF-8"); // the C locale will be the UTF-8 enabled English
    setlocale(LC_NUMERIC, "de_DE");   // decimal dot will be German
    setlocale(LC_TIME, "ja_JP");      // date/time formatting will be Japanese
    wchar_t str[100];
    time_t t = time(NULL);
    wcsftime(str, 100, L"%A %c", localtime(&t));
    wprintf(L"Number: %.2f\nDate: %Ls\n", 3.14, str);


Number: 3,14
Date: 月曜日 2011年12月19日 18時04分40秒

[edit] See also

gets and sets the current C locale
C++ documentation for locale categories