duplocale - duplicate a locale object

       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).

ENOMEM Insufficient memory to create the duplicate locale object.

       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.outabc
           ABC

   Programsource

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

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

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

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

           printf("\n");

           freelocale(nloc);

           exit(EXIT_SUCCESS);
       }

       glibc 2.3.

       Standard C library (libc, -lc)

       duplocale - duplicate a locale object

       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 EXAMPLES, below.

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

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

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

Linux man-pages 6.9.1                              2024-06-15                                       duplocale(3)

       POSIX.1-2008.

#include<locale.h>locale_tduplocale(locale_tlocobj);

   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