duplocale(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | EXAMPLES | 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 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 EXAMPLES, below.

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

EXAMPLES         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;

           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);
       }

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.12 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                          2021-03-22                   DUPLOCALE(3)

Pages that refer to this page: isalpha(3)newlocale(3)strfmon(3)toupper(3)towlower(3)towupper(3)uselocale(3)locale(7)