Manpages - duplocale.3p

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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.


duplocale — duplicate a locale object


  #include <locale.h>
  locale_t duplocale(locale_t locobj);


The duplocale/() function shall create a duplicate copy of the locale object referenced by the /locobj argument.

If the locobj argument is LC_GLOBAL_LOCALE, /duplocale/() shall create a new locale object containing a copy of the global locale determined by the /setlocale/() function.

The behavior is undefined if the locobj argument is not a valid locale object handle.


Upon successful completion, the /duplocale/() function shall return a handle for a new locale object. Otherwise, duplocale/() shall return ( locale_t)0 and set /errno to indicate the error.


The /duplocale/() function shall fail if:

There is not enough memory available to create the locale object or load the locale data.

The following sections are informative.


Constructing an Altered Version of an Existing Locale Object

The following example shows a code fragment to create a slightly altered version of an existing locale object. The function takes a locale object and a locale name and it replaces the LC_TIME category data in the locale object with that from the named locale.

    #include <locale.h>
    with_changed_lc_time (locale_t obj, const char *name)
        locale_t retval = duplocale (obj);
        if (retval != (locale_t) 0)
            locale_t changed = newlocale (LC_TIME_MASK, name, retval);
            if (changed == (locale_t) 0)
                /* An error occurred. Free all allocated resources. */
                freelocale (retval);
            retval = changed;
        return retval;


The use of the /duplocale/() function is recommended for situations where a locale object is being used in multiple places, and it is possible that the lifetime of the locale object might end before all uses are finished. Another reason to duplicate a locale object is if a slightly modified form is needed. This can be achieved by a call to /newlocale/() following the /duplocale/() call.

As with the /newlocale/() function, handles for locale objects created by the /duplocale/() function should be released by a corresponding call to /freelocale/().

The /duplocale/() function can also be used in conjunction with /uselocale/(( locale_t)0). This returns the locale in effect for the calling thread, but can have the value LC_GLOBAL_LOCALE. Passing LC_GLOBAL_LOCALE to functions such as /isalnum_l/() results in undefined behavior, but applications can convert it into a usable locale object by using /duplocale/().






/freelocale ( )/, /newlocale ( )/, /uselocale ( )/

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


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 .

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 .

Author: dt

Created: 2022-02-20 Sun 09:16