focal (3) duplocale.3.gz

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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