NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON

DUPLOCALE(3)              Linux Programmer's Manual             DUPLOCALE(3)

NAME         top

       duplocale - duplicate a locale object

SYNOPSIS         top

       #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         top

       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         top

       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         top

       ENOMEM Insufficient memory to create the duplicate locale object.

VERSIONS         top

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

CONFORMING TO         top

       POSIX.1-2008.

NOTES         top

       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         top

       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         top

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

COLOPHON         top

       This page is part of release 4.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

Linux                            2014-03-12                     DUPLOCALE(3)