towlower - Man Page

transliterate uppercase wide-character code to lowercase


This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.


#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.1-2017 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 locale used by the function 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.

Return Value

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.



Application Usage




Future Directions


See Also

setlocale(), uselocale()

The Base Definitions volume of POSIX.1-2017, Chapter 7, Locale, <locale.h>, <wctype.h>

Referenced By

setlocale(3p), towctrans(3p), wchar.h(0p), wctype.h(0p).

2017 IEEE/The Open Group POSIX Programmer's Manual