.\" Copyright (c) 1989, 1991, 1993
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.\"	@(#)tolower.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: head/lib/libc/locale/tolower.3 210468 2010-07-25 13:32:19Z bcr $
.\"
.Dd December 25, 2013
.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
.Fn tolower "int c"
.Ft int
.Fn tolower_l "int c" "locale_t locale"
.Sh DESCRIPTION
The
.Fn tolower
and
.Fn tolower_l
functions convert 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
The _l-suffixed version takes an explicit
.Fa locale
argument, whereas the
non-suffixed version uses the current global or per-thread locale.
.Sh RETURN VALUES
If the argument is an upper-case letter, the
.Fn tolower
and
.Fn tolower_l
functions return 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
and
.Fn towlower_l
functions should be used instead.
.Sh SEE ALSO
.Xr ctype 3 ,
.Xr ctype_l 3 ,
.Xr islower 3 ,
.Xr towlower 3 ,
.Xr towlower_l 3 ,
.Xr xlocale 3
.Sh STANDARDS
The
.Fn tolower
function conforms to
.St -isoC .
The
.Fn tolower_l
function conforms to
.St -p1003.1-2008 .