NAME

       duplocale - duplicate a locale object

SYNOPSIS

       #include <locale.h>

       locale_t duplocale(locale_t locobj);

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

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

DESCRIPTION

       The duplocale() function creates a duplicate of the locale object referred to by locobj.

       If  locobj  is  LC_GLOBAL_LOCALE, duplocale() creates a locale object containing a copy of
       the global locale determined by setlocale(3).

RETURN VALUE

       On success, duplocale() returns a handle for the new locale object.  On error, it  returns
       (locale_t) 0, and sets errno to indicate the cause of the error.

ERRORS

       ENOMEM Insufficient memory to create the duplicate locale object.

VERSIONS

       The duplocale() function first appeared in version 2.3 of the GNU C library.

CONFORMING TO

       POSIX.1-2008.

NOTES

       Duplicating a locale can serve the following purposes:

       *  To  create a copy of a locale object in which one of more categories are to be modified
          (using newlocale(3)).

       *  To obtain a handle for the current locale which can used in other functions that employ
          a  locale  handle,  such  as toupper_l(3).  This is done by applying duplocale() to the
          value returned by the following call:

              loc = uselocale((locale_t) 0);

          This technique is necessary, because the above uselocale(3) call may return  the  value
          LC_GLOBAL_LOCALE,  which  results  in undefined behavior if passed to functions such as
          toupper_l(3).  Calling duplocale() can be used  to  ensure  that  the  LC_GLOBAL_LOCALE
          value is converted into a usable locale object.  See EXAMPLE, below.

       Each locale object created by duplocale() should be deallocated using freelocale(3).

EXAMPLE

       The  program  below  uses  uselocale(3) and duplocale() to obtain a handle for the current
       locale which is then passed to toupper_l(3).  The program takes one command-line argument,
       a  string  of  characters that is converted to uppercase and displayed on standard output.
       An example of its use is the following:

           $ ./a.out abc
           ABC

   Program source
       #define _XOPEN_SOURCE 700
       #include <ctype.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <locale.h>

       #define errExit(msg)    do { perror(msg); exit(EXIT_FAILURE); \
                               } while (0)

       int
       main(int argc, char *argv[])
       {
           locale_t loc, nloc;
           char *p;

           if (argc != 2) {
               fprintf(stderr, "Usage: %s string\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           /* This sequence is necessary, because uselocale() might return
              the value LC_GLOBAL_LOCALE, which can't be passed as an
              argument to toupper_l() */

           loc = uselocale((locale_t) 0);
           if (loc == (locale_t) 0)
               errExit("uselocale");

           nloc = duplocale(loc);
           if (nloc == (locale_t) 0)
               errExit("duplocale");

           for (p = argv[1]; *p; p++)
               putchar(toupper_l(*p, nloc));

           printf("\n");

           freelocale(nloc);

           exit(EXIT_SUCCESS);
       }

SEE ALSO

       freelocale(3), newlocale(3), setlocale(3), uselocale(3), locale(5), locale(7)

COLOPHON

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