USELOCALE(3)               POSIX Programmer's Manual              USELOCALE(3)



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

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 .



IEEE/The Open Group                  2017                         USELOCALE(3)
