setlocale, _wsetlocale

Article
04/28/2015

Sets or retrieves the run-time locale.

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

Parameters

category
Category affected by locale.
locale
Locale specifier.

Return Value

If a valid locale and category are given, returns a pointer to the string associated with the specified locale and category. If the locale or category is not valid, returns a null pointer and the current locale settings of the program are not changed.

For example, the call

setlocale( LC_ALL, "en-US" );

sets all categories, returning only the string

en-US

You can copy the string returned by setlocale to restore that part of the program's locale information. Global or thread local storage is used for the string returned by setlocale. Later calls to setlocale overwrite the string, which invalidates string pointers returned by earlier calls.

Remarks

Use the setlocale function to set, change, or query some or all of the current program locale information specified by locale and category. locale refers to the locality (country/region and language) for which you can customize certain aspects of your program. Some locale-dependent categories include the formatting of dates and the display format for monetary values. If you set locale to the default string for a language that has multiple forms supported on your computer, you should check the setlocale return value to see which language is in effect. For example, if you set locale to "chinese" the return value could be either "chinese-simplified" or "chinese-traditional".

_wsetlocale is a wide-character version of setlocale; the locale argument and return value of _wsetlocale are wide-character strings. _wsetlocale and setlocale behave identically otherwise.

Generic-Text Routine Mappings

TCHAR.H routine	_UNICODE & _MBCS not defined	_MBCS defined	_UNICODE defined
_tsetlocale	setlocale	setlocale	_wsetlocale

The category argument specifies the parts of a program's locale information that are affected. The macros used for category and the parts of the program they affect are as follows:

LC_ALL
All categories in the following list.
LC_COLLATE
The strcoll, _stricoll, wcscoll, _wcsicoll, strxfrm, _strncoll, _strnicoll, _wcsncoll, _wcsnicoll, and wcsxfrm functions.
LC_CTYPE
The character-handling functions (except isdigit, isxdigit, mbstowcs, and mbtowc, which are unaffected).
LC_MONETARY
Monetary-formatting information returned by the localeconv function.
LC_NUMERIC
Decimal-point character for the formatted output routines (such as printf), for the data-conversion routines, and for the non-monetary formatting information returned by localeconv. In addition to the decimal-point character, LC_NUMERIC also sets the thousands separator and the grouping control string returned by localeconv.
LC_TIME
The strftime and wcsftime functions.

This function validates the category parameter. If the category parameter is not one of the values given in the previous table, the invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, the function sets errno to EINVAL and returns NULL.

The locale argument is a pointer to a string that specifies the locale. For information about the format of the locale argument, see Locale Names, Languages, and Country/Region Strings. If locale points to an empty string, the locale is the implementation-defined native environment. A value of C specifies the minimal ANSI conforming environment for C translation. The C locale assumes that all char data types are 1 byte and that their value is always less than 256.

At program startup, the equivalent of the following statement is executed:

setlocale( LC_ALL, "C" );

The locale argument can take a locale name, a language string, a language string and country/region code, a code page, or a language string, country/region code, and code page. The set of available locale names, languages, country/region codes, and code pages includes all those supported by the Windows NLS API except code pages that require more than two bytes per character, such as UTF-7 and UTF-8. If you provide a code page value of UTF-7 or UTF-8, setlocale will fail, returning NULL. The set of locale names supported by setlocale are described in Locale Names, Languages, and Country/Region Strings. The set of language and country/region strings supported by setlocale are listed in Language Strings and Country/Region Strings. We recommend the locale name form for performance and for maintainability of locale strings embedded in code or serialized to storage. The locale name strings are less likely to be changed by an operating system update than the language and country/region name form.

A null pointer that's passed as the locale argument tells setlocale to query instead of to set the international environment. If the locale argument is a null pointer, the program's current locale setting is not changed. Instead, setlocale returns a pointer to the string that's associated with the category of the thread's current locale. If the category argument is LC_ALL, the function returns a string that indicates the current setting of each category, separated by semicolons. For example, the sequence of calls

// Set all categories and return "en-US"

setlocale(LC_ALL, "en-US");

// Set only the LC_MONETARY category and return "fr-FR"

setlocale(LC_MONETARY, "fr-FR");

printf("%s\n", setlocale(LC_ALL, NULL));

returns

LC_COLLATE=en-US;LC_CTYPE=en-US;LC_MONETARY=fr-FR;LC_NUMERIC=en-US;LC_TIME=en-US

which is the string that's associated with the LC_ALL category.

The following examples pertain to the LC_ALL category. Either of the strings ".OCP" and ".ACP" can be used instead of a code page number to specify use of the user-default OEM code page and user-default ANSI code page, respectively.

setlocale( LC_ALL, "" );
Sets the locale to the default, which is the user-default ANSI code page obtained from the operating system.
setlocale( LC_ALL, ".OCP" );
Explicitly sets the locale to the current OEM code page obtained from the operating system.
setlocale( LC_ALL, ".ACP" );
Sets the locale to the ANSI code page obtained from the operating system.
setlocale( LC_ALL, "<localename>" );
Sets the locale to the locale name that's indicated by <localename>.
setlocale( LC_ALL, "<language>_<country>" );
Sets the locale to the language and country/region indicated by <language> and <country>, together with the default code page obtained from the host operating system.
setlocale( LC_ALL, "<language>_<country>.<code_page>" );
Sets the locale to the language, country/region, and code page indicated by the <language>, <country>, and <code_page> strings. You can use various combinations of language, country/region, and code page. For example, this call sets the locale to French Canada with code page 1252:

setlocale( LC_ALL, "French_Canada.1252" );

This call sets the locale to French Canada with the default ANSI code page:

setlocale( LC_ALL, "French_Canada.ACP" );

This call sets the locale to French Canada with the default OEM code page:

setlocale( LC_ALL, "French_Canada.OCP" );
setlocale( LC_ALL, "<language>" );
Sets the locale to the language that's indicated by <language>, and uses the default country/region for the specified language and the user-default ANSI code page for that country/region as obtained from the host operating system. For example, the following calls to setlocale are functionally equivalent:

setlocale( LC_ALL, "en-US" );

setlocale( LC_ALL, "English" );

setlocale( LC_ALL, "English_United States.1252" );

We recommend the first form for performance and maintainability.
setlocale( LC_ALL, ".<code_page>" );
Sets the code page to the value indicated by <code_page>, together with the default country/region and language (as defined by the host operating system) for the specified code page.

The category must be either LC_ALL or LC_CTYPE to effect a change of code page. For example, if the default country/region and language of the host operating system are "United States" and "English," the following two calls to setlocale are functionally equivalent:

setlocale( LC_ALL, ".1252" );

setlocale( LC_ALL, "English_United States.1252");

For more information, see the setlocale pragma directive in the C/C++ Preprocessor Reference.

The function _configthreadlocale is used to control whether setlocale affects the locale of all threads in a program or only the locale of the calling thread.

Requirements

Routine	Required header
setlocale	<locale.h>
_wsetlocale	<locale.h> or <wchar.h>

For additional compatibility information, see Compatibility in the Introduction.

Example

// crt_setlocale.c
// 
// This program demonstrates the use of setlocale when
// using two independent threads.
//

#include <locale.h>
#include <process.h>
#include <windows.h>
#include <stdio.h>
#include <time.h>

#define BUFF_SIZE 100

// Retrieve the date in the current
// locale's format.
int get_date(unsigned char* str)
{
    __time64_t ltime;
    struct tm  thetime;

    // Retrieve the current time
    _time64(&ltime);
    _gmtime64_s(&thetime, &ltime);

    // Format the current time structure into a string
    // "%#x" is the long date representation in the
    // current locale
    if (!strftime((char *)str, BUFF_SIZE, "%#x", 
                  (const struct tm *)&thetime))
    {
        printf("strftime failed!\n");
        return -1;
    }
    return 0;
}

// This thread sets its locale to the argument
// and prints the date.
uintptr_t __stdcall SecondThreadFunc( void* pArguments )
{
    unsigned char str[BUFF_SIZE];
    char * locale = (char *)pArguments;

    // Set the thread locale
    printf("The thread locale is now set to %s.\n",
           setlocale(LC_ALL, locale));

    // Retrieve the date string from the helper function
    if (get_date(str) == 0)
    {
        printf("The date in %s locale is: '%s'\n", locale, str);
    }

    _endthreadex( 0 );
    return 0;
} 

// The main thread sets the locale to English 
// and then spawns a second thread (above) and prints the date.
int main()
{ 
    HANDLE          hThread;
    unsigned        threadID;
    unsigned char   str[BUFF_SIZE];

    // Configure per-thread locale to cause all subsequently created 
    // threads to have their own locale.
    _configthreadlocale(_ENABLE_PER_THREAD_LOCALE);

    // Set the locale of the main thread to US English.
    printf("The thread locale is now set to %s.\n",
           setlocale(LC_ALL, "en-US"));

    // Create the second thread with a German locale.
    // Our thread function takes an argument of the locale to use.
    hThread = (HANDLE)_beginthreadex( NULL, 0, &SecondThreadFunc,
                                      "de-DE", 0, &threadID );

    if (get_date(str) == 0)
    {
        // Retrieve the date string from the helper function
        printf("The date in en-US locale is: '%s'\n\n", str);
    }

    // Wait for the created thread to finish.
    WaitForSingleObject( hThread, INFINITE );

    // Destroy the thread object.
    CloseHandle( hThread );
}

The thread locale is now set to en-US.
The time in en-US locale is: 'Wednesday, May 12, 2004'

The thread locale is now set to de-DE.
The time in de-DE locale is: 'Mittwoch, 12. Mai 2004'

.NET Framework Equivalent

System::Globalization::CultureInfo Class