char *setlocale(int category, const char *locale);

The setlocale() function is used to change or query part or all of the current locale. The effect of the category argument for each value is:

A value of "C" for locale specifies the minimal environment for C translation. An empty string, "", for locale specifies the implementation-defined native environment. At program startup, the equivalent of setlocale(LC_ALL, "C") is executed.

Valid locale values depend on which __use_X_ctype symbols are imported (__use_iso8859_ctype, __use_sjis_ctype, __use_utf8_ctypte), and on user-defined locales.

If a pointer to a string is given for locale and the selection is valid, the string associated with the specified category for the new locale is returned. If the selection cannot be honored, a null pointer is returned and the locale is not changed.

A null pointer for locale causes the string associated with the category for the current locale to be returned and the locale is not changed.

If category is LC_ALL and the most recent successful locale-setting call uses a category other than LC_ALL, a composite string might be returned. The string returned when used in a subsequent call with its associated category restores that part of the program locale. The string returned is not modified by the program, but might be overwritten by a subsequent call to setlocale().