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2019-03-06
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Linux kernel and C library user-space interface documentation
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:
Each locale object created by duplocale() should be deallocated using freelocale(3).
| * | 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. |
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)
} while (0)
int main(int argc, char *argv[]) {
locale_t loc, nloc;
char *p;
locale_t loc, nloc;
char *p;
if (argc != 2) {
fprintf(stderr, "Usage: %s string\n", argv[0]);
exit(EXIT_FAILURE);
}
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\(aqt be passed as an
argument to toupper_l() */
the value LC_GLOBAL_LOCALE, which can\(aqt be passed as an
argument to toupper_l() */
loc = uselocale((locale_t) 0);
if (loc == (locale_t) 0)
errExit("uselocale");
if (loc == (locale_t) 0)
errExit("uselocale");
nloc = duplocale(loc);
if (nloc == (locale_t) 0)
errExit("duplocale");
if (nloc == (locale_t) 0)
errExit("duplocale");
for (p = argv[1]; *p; p++)
putchar(toupper_l(*p, nloc));
putchar(toupper_l(*p, nloc));
printf("\n");
freelocale(nloc);
exit(EXIT_SUCCESS); }
