How Programs Set the Locale
===========================
A C program inherits its locale environment variables when it starts
up. This happens automatically. However, these variables do not
automatically control the locale used by the library functions, because
ISO C says that all programs start by default in the standard `C'
locale. To use the locales specified by the environment, you must call
`setlocale'. Call it as follows:
setlocale (LC_ALL, "");
to select a locale based on the user choice of the appropriate
environment variables.
You can also use `setlocale' to specify a particular locale, for
general use or for a specific category.
The symbols in this section are defined in the header file
`locale.h'.
- Function: char * setlocale (int CATEGORY, const char *LOCALE)
The function `setlocale' sets the current locale for category
CATEGORY to LOCALE. A list of all the locales the system provides
can be created by running
locale -a
If CATEGORY is `LC_ALL', this specifies the locale for all
purposes. The other possible values of CATEGORY specify an single
purpose (Note:Locale Categories).
You can also use this function to find out the current locale by
passing a null pointer as the LOCALE argument. In this case,
`setlocale' returns a string that is the name of the locale
currently selected for category CATEGORY.
The string returned by `setlocale' can be overwritten by subsequent
calls, so you should make a copy of the string (Note:Copying and
Concatenation) if you want to save it past any further calls to
`setlocale'. (The standard library is guaranteed never to call
`setlocale' itself.)
You should not modify the string returned by `setlocale'. It might
be the same string that was passed as an argument in a previous
call to `setlocale'. One requirement is that the CATEGORY must be
the same in the call the string was returned and the one when the
string is passed in as LOCALE parameter.
When you read the current locale for category `LC_ALL', the value
encodes the entire combination of selected locales for all
categories. In this case, the value is not just a single locale
name. In fact, we don't make any promises about what it looks
like. But if you specify the same "locale name" with `LC_ALL' in
a subsequent call to `setlocale', it restores the same combination
of locale selections.
To be sure you can use the returned string encoding the currently
selected locale at a later time, you must make a copy of the
string. It is not guaranteed that the returned pointer remains
valid over time.
When the LOCALE argument is not a null pointer, the string returned
by `setlocale' reflects the newly-modified locale.
If you specify an empty string for LOCALE, this means to read the
appropriate environment variable and use its value to select the
locale for CATEGORY.
If a nonempty string is given for LOCALE, then the locale of that
name is used if possible.
If you specify an invalid locale name, `setlocale' returns a null
pointer and leaves the current locale unchanged.
Here is an example showing how you might use `setlocale' to
temporarily switch to a new locale.
#include <stddef.h>
#include <locale.h>
#include <stdlib.h>
#include <string.h>
void
with_other_locale (char *new_locale,
void (*subroutine) (int),
int argument)
{
char *old_locale, *saved_locale;
/* Get the name of the current locale. */
old_locale = setlocale (LC_ALL, NULL);
/* Copy the name so it won't be clobbered by `setlocale'. */
saved_locale = strdup (old_locale);
if (saved_locale == NULL)
fatal ("Out of memory");
/* Now change the locale and do some stuff with it. */
setlocale (LC_ALL, new_locale);
(*subroutine) (argument);
/* Restore the original locale. */
setlocale (LC_ALL, saved_locale);
free (saved_locale);
}
*Portability Note:* Some ISO C systems may define additional locale
categories, and future versions of the library will do so. For
portability, assume that any symbol beginning with `LC_' might be
defined in `locale.h'.