std::setlocale

 

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Localizations library

Locales and facets
locale
use_facet	has_facet
Character classification
isspace isblank (C++11) iscntrl isupper islower isalpha	isdigit ispunct isxdigit isalnum isprint isgraph
Conversions
toupper tolower	wstring_convert (C++11) wbuffer_convert (C++11)
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
Facet categories
ctype ctype<char> codecvt collate messages time_get time_put	num_get num_put numpunct money_get money_put moneypunct
Locale-specific facets
ctype_byname ctype_byname<char> codecvt_byname messages_byname collate_byname	time_get_byname time_put_byname numpunct_byname moneypunct_byname
Code conversion facets
codecvt_utf8 (C++11) codecvt_utf16 (C++11)	codecvt_utf8_utf16 (C++11) codecvt_mode (C++11)
C locale
setlocale localeconv lconv	LC_ALL LC_COLLATE LC_CTYPE LC_MONETARY LC_NUMERIC LC_TIME

 

Defined in header <clocale>
char* setlocale( int category, const char* locale);

The setlocale function installs the specified system locale or its portion as the new C locale. The modifications remain in effect and influences the execution of all locale-sensitive C library functions until the next call to setlocale. If locale is a null pointer, setlocale queries the current C locale without modifying it.

Parameters

category	-	locale category identifier, one of the LC_xxx macros. May be null.
locale	-	system-specific locale identifier. Can be "" for the user-preferred locale or "C" for the minimal locale

Return value

Pointer to a narrow null-terminated string identifying the C locale after applying the changes, if any, or null pointer on failure.

Notes

During program startup, the equivalent of std::setlocale(LC_ALL, "C"); is executed before any user code is run.

Although the return type is char*, modifying the pointed-to characters is undefined behavior.

Because setlocale modifies global state which affects execution of locale-dependent functions, it is undefined behavior to call it from one thread, while another thread is executing any of the following functions: std::fprintf, std::isprint, std::iswdigit, std::localeconv, std::tolower, std::fscanf, std::ispunct, std::iswgraph, std::mblen, std::toupper, std::isalnum, std::isspace, std::iswlower, std::mbstowcs, std::towlower, std::isalpha, std::isupper, std::iswprint, std::mbtowc, std::towupper, std::isblank, std::iswalnum, std::iswpunct, std::setlocale, std::wcscoll, std::iscntrl, std::iswalpha, std::iswspace, std::strcoll, std::wcstod, std::isdigit, std::iswblank, std::iswupper, std::strerror, std::wcstombs, std::isgraph, std::iswcntrl, std::iswxdigit, std::strtod, std::wcsxfrm, std::islower, std::iswctype, std::isxdigit.

Example

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

Output:

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

See also

LC_ALL LC_COLLATE LC_CTYPE LC_MONETARY LC_NUMERIC LC_TIME	locale categories for std::setlocale (macro constant)
locale	set of polymorphic facets that encapsulate cultural differences (class)
C documentation for setlocale