duplocale - duplicate a locale object
#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 cause of the error.
- ENOMEM
- Insufficient memory to create the duplicate locale object.
The
duplocale() function first appeared in version 2.3 of the GNU C
library.
POSIX.1-2008.
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).
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
#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);
}
freelocale(3),
newlocale(3),
setlocale(3),
uselocale(3),
locale(5),
locale(7)