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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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duplocale(3) Library Functions Manual duplocale(3)
duplocale - duplicate a locale object
Standard C library (libc, -lc)
#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
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).
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.
ENOMEM Insufficient memory to create the duplicate locale object.
POSIX.1-2008.
glibc 2.3.
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).
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 <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);
}
freelocale(3), newlocale(3), setlocale(3), uselocale(3),
locale(5), locale(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.15 2025-05-17 duplocale(3)
Pages that refer to this page: isalpha(3), locale_t(3type), newlocale(3), strfmon(3), toupper(3), towlower(3), towupper(3), uselocale(3), locale(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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