duplocale(3)

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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