duplocale man page

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duplocale — duplicate a locale object

Synopsis

#include <locale.h>

locale_t duplocale(locale_t locobj);

Description

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.

Return Value

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.

Errors

The duplocale() function shall fail if:

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

The following sections are informative.

Examples

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>
...

locale_t
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; }
}

Application Usage

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().

See Also

freelocale(), newlocale(), uselocale()

The Base Definitions volume of POSIX.1‐2008, <locale.h>

Info

2013 IEEE/The Open Group POSIX Programmer's Manual