towlower man page
towlower, towlower_l — transliterate uppercase wide-character code to lowercase
#include <wctype.h> wint_t towlower(wint_t wc); wint_t towlower_l(wint_t wc, locale_t locale);
For towlower(): The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.
The towlower() and towlower_l() functions have as a domain a type wint_t, the value of which the application shall ensure is a character representable as a wchar_t, and a wide-character code corresponding to a valid character in the current locale or the value of WEOF. If the argument has any other value, the behavior is undefined. If the argument of towlower() or towlower_l() represents an uppercase wide-character code, and there exists a corresponding lowercase wide-character code as defined by character type information in the current locale or in the locale represented by locale, respectively (category LC_CTYPE), the result shall be the corresponding lowercase wide-character code. All other arguments in the domain are returned unchanged.
The behavior is undefined if the locale argument to towlower_l() is the special locale object LC_GLOBAL_LOCALE or is not a valid locale object handle.
Upon successful completion, the towlower() and towlower_l() functions shall return the lowercase letter corresponding to the argument passed; otherwise, they shall return the argument unchanged.
No errors are defined.
The following sections are informative.
The Base Definitions volume of POSIX.1-2008, Chapter 7, Locale, <locale.h>, <wctype.h>
setlocale(3p), towctrans(3p), wchar.h(0p), wctype.h(0p).