uselocale - set/get the locale for the calling thread

       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).

EINVALnewloc does not refer to a valid locale object.

       See newlocale(3) and duplocale(3).

       glibc 2.3.  POSIX.1-2008.

       Standard C library (libc, -lc)

       uselocale - set/get the locale for the calling thread

       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.

       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 error.

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

Linux man-pages 6.9.1                              2024-05-02                                       uselocale(3)

       POSIX.1-2008.

#include<locale.h>locale_tuselocale(locale_tnewloc);

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

       uselocale():
           Since glibc 2.10:
               _XOPEN_SOURCE >= 700
           Before glibc 2.10:
               _GNU_SOURCE