towlower(3)		    Library Functions Manual		     towlower(3)

NAME
     towlower, towlower_l - convert a wide character to lowercase

LIBRARY
     Standard C library (libc, -lc)

SYNOPSIS
     #include <wctype.h>

     wint_t towlower(wint_t wc);
     wint_t towlower_l(wint_t wc, locale_t locale);

 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

     towlower_l():
	 Since glibc 2.10:
	     _XOPEN_SOURCE >= 700
	 Before glibc 2.10:
	     _GNU_SOURCE

DESCRIPTION
     The  towlower() function is the wide-character equivalent of the tolower(3)
     function.	If wc is an uppercase wide character, and there exists a  lower-
     case  equivalent in the current locale, it returns the lowercase equivalent
     of wc.  In all other cases, wc is returned unchanged.

     The towlower_l() function performs the same task, but performs the	 conver-
     sion based on the character type information in the locale specified by lo-
     cale.   The  behavior of towlower_l() is undefined if locale is the special
     locale object LC_GLOBAL_LOCALE (see duplocale(3)) or is not a valid  locale
     object handle.

     The argument wc must be representable as a wchar_t and be a valid character
     in the locale or be the value WEOF.

RETURN VALUE
     If wc was convertible to lowercase, towlower() returns its lowercase equiv-
     alent; otherwise it returns wc.

ATTRIBUTES
     For  an  explanation  of the terms used in this section, see attributes(7).
     allbox; lbx lb lb l l l.  Interface Attribute Value T{ towlower()
     T}	  Thread safety	  MT-Safe locale T{ towlower_l() T}   Thread safety  MT-
     Safe

STANDARDS
     towlower()
	    C11, POSIX.1-2008 (XSI).

     towlower_l()
	    POSIX.1-2008.

STANDARDS
     towlower()
	    C99, POSIX.1-2001 (XSI).  Obsolete in POSIX.1-2008 (XSI).

     towlower_l()
	    glibc 2.3.	POSIX.1-2008.

NOTES
     The behavior of these functions depends on the LC_CTYPE category of the lo-
     cale.

     These functions are not very appropriate for dealing with	Unicode	 charac-
     ters,  because  Unicode  knows  about  three cases: upper, lower, and title
     case.

SEE ALSO
     iswlower(3), towctrans(3), towupper(3), locale(7)

Linux man-pages 6.18		   2026-02-08			     towlower(3)