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.\"	@(#)tolower.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/locale/tolower.3,v 1.21 2009/09/04 07:44:58 des Exp $
.\"
.Dd July 17, 2005
.Dt TOLOWER 3
.Os
.Sh NAME
.Nm tolower ,
.Nm tolower_l
.Nd upper case to lower case letter conversion
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In ctype.h
.Ft int
.Fo tolower
.Fa "int c"
.Fc
.In ctype.h
.In xlocale.h
.Ft int
.Fo tolower_l
.Fa "int c"
.Fa "locale_t loc"
.Fc
.Sh DESCRIPTION
The
.Fn tolower
function converts an upper-case letter to the corresponding lower-case
letter.
The argument must be representable as an
.Vt "unsigned char"
or the value of
.Dv EOF .
.Pp
Although the
.Fn tolower
function uses the current locale, the
.Fn tolower_l
function may be passed a locale directly. See
.Xr xlocale 3
for more information.
.Sh RETURN VALUES
If the argument is an upper-case letter, the
.Fn tolower
function returns the corresponding lower-case letter if there is
one; otherwise, the argument is returned unchanged.
.Sh COMPATIBILITY
The
.Bx 4.4
extension of accepting arguments outside of the range of the
.Vt "unsigned char"
type in locales with large character sets is considered obsolete
and may not be supported in future releases.
The
.Fn towlower
function should be used instead.
.Sh SEE ALSO
.Xr ctype 3 ,
.Xr islower 3 ,
.Xr towlower 3 ,
.Xr xlocale 3
.Sh STANDARDS
The
.Fn tolower
function conforms to
.St -isoC .