#include <wctype.h> wctrans_t wctrans(const char *charclass);
The wctrans() function is defined for valid character mapping names identified in the current locale. The charclass is a string identifying a generic character mapping name for which codeset-specific information is required. The following character mapping names are defined in all locales − "tolower" and "toupper".
The function returns a value of type wctrans_t, which can be used as the second argument to subsequent calls of towctrans(3C). The wctrans() function determines values of wctrans_t according to the rules of the coded character set defined by character mapping information in the program's locale (category LC_CTYPE). The values returned by wctrans() are valid until a call to setlocale(3C) that modifies the category LC_CTYPE.
The wctrans() function returns 0 if the given character mapping name is not valid for the current locale (category LC_CTYPE), otherwise it returns a non-zero object of type wctrans_t that can be used in calls to towctrans(3C).
The wctrans() function may fail if:
The character mapping name pointed to by charclass is not valid in the current locale.
See attributes(5) for descriptions of the following attributes: