uselocale — set/get the locale for the calling thread


#include <locale.h>

locale_t uselocale(locale_t newloc);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):


Since glibc 2.10:


Before glibc 2.10:



The uselocale() function sets the current locale for the calling thread, and returns the thread's previously current locale. After a successful call to uselocale(), any calls by this thread to functions that depend on the locale will operate as though the locale has been set to newloc.

The newloc argument can have one of the following values:

A handle returned by a call to newlocale(3) or duplocale(3)

The calling thread's current locale is set to the specified locale.

The special locale object handle LC_GLOBAL_LOCALE

The calling thread's current locale is set to the global locale determined by setlocale(3).

(locale_t) 0

The calling thread's current locale is left unchanged (and the current locale is returned as the function result).

Return Value

On success, uselocale() returns the locale handle that was set by the previous call to uselocale() in this thread, or LC_GLOBAL_LOCALE if there was no such previous call. On error, it returns (locale_t) 0, and sets errno to indicate the cause of the error.



newloc does not refer to a valid locale object.


The uselocale() function first appeared in version 2.3 of the GNU C library.

Conforming to



Unlike setlocale(3), uselocale() does not allow selective replacement of individual locale categories. To employ a locale that differs in only a few categories from the current locale, use calls to duplocale(3) and newlocale(3) to obtain a locale object equivalent to the current locale and modify the desired categories in that object.


See newlocale(3) and duplocale(3).

See Also

locale(1), duplocale(3), freelocale(3), newlocale(3), setlocale(3), locale(5), locale(7)


This page is part of release 5.04 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at

Referenced By

duplocale(3), isalpha(3), locale(5), locale(7), newlocale(3), toupper(3).

2017-09-15 Linux Programmer's Manual