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       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       uselocale — use locale in current thread

SYNOPSIS

       #include <locale.h>

       locale_t uselocale(locale_t newloc);

DESCRIPTION

       The uselocale() function shall set or query the current locale for the calling thread.

       The value for the newloc argument shall be one of the following:

        1. A value returned by the newlocale() or duplocale() functions

        2. The special locale object descriptor LC_GLOBAL_LOCALE

        3. (locale_t)0

       If the newloc argument is (locale_t)0, the current locale shall not be changed; this value
       can  be  used  to  query  the  current  locale  setting.  If  the   newloc   argument   is
       LC_GLOBAL_LOCALE, any thread-local locale for the calling thread shall be uninstalled; the
       thread shall again use the global locale as the current locale, and changes to the  global
       locale  shall  affect  the  thread.  Otherwise,  the locale represented by newloc shall be
       installed as a thread-local locale to be used  as  the  current  locale  for  the  calling
       thread.

       Once  the  uselocale()  function  has  been  called  to install a thread-local locale, the
       behavior of every interface using data from the current locale shall be affected  for  the
       calling thread. The current locale for other threads shall remain unchanged.

RETURN VALUE

       Upon successful completion, the uselocale() function shall return a handle for the thread-
       local locale that was in use as the current locale for the calling thread on entry to  the
       function, or LC_GLOBAL_LOCALE if no thread-local locale was in use. Otherwise, uselocale()
       shall return (locale_t)0 and set errno to indicate the error.

ERRORS

       The uselocale() function may fail if:

       EINVAL newloc is not a valid locale object and is not (locale_t)0.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       Unlike the setlocale() function, the uselocale() function does not  allow  replacing  some
       locale categories only. Applications that need to install a locale which differs only in a
       few categories must use newlocale() to change a locale object equivalent to the  currently
       used locale and install it.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       duplocale(), freelocale(), newlocale(), setlocale()

       The Base Definitions volume of POSIX.1‐2017, <locale.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1-2017, Standard for Information Technology -- Portable  Operating  System  Interface
       (POSIX),  The  Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
       the Institute of Electrical and Electronics Engineers, Inc and The  Open  Group.   In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any  typographical  or  formatting errors that appear in this page are most likely to have
       been introduced during the conversion of the source files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .