opendarwin man page for duplocale

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

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:

       *  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 con-
	  verted into a usable locale object.  See EXAMPLE, below.

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

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  exam-
       ple 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
", 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("
");

	   freelocale(nloc);

	   exit(EXIT_SUCCESS);
       }

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

COLOPHON
       This  page is part of release 4.15 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								    2017-09-15							      DUPLOCALE(3)