1.\" Copyright (c) 1989, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)tolower.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd July 25, 2010 36.Dt TOLOWER 3 37.Os 38.Sh NAME 39.Nm tolower 40.Nd upper case to lower case letter conversion 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In ctype.h 45.Ft int 46.Fn tolower "int c" 47.Sh DESCRIPTION 48The 49.Fn tolower 50function converts an upper-case letter to the corresponding lower-case 51letter. 52The argument must be representable as an 53.Vt "unsigned char" 54or the value of 55.Dv EOF . 56.Sh RETURN VALUES 57If the argument is an upper-case letter, the 58.Fn tolower 59function returns the corresponding lower-case letter if there is 60one; otherwise, the argument is returned unchanged. 61.Sh COMPATIBILITY 62The 63.Bx 4.4 64extension of accepting arguments outside of the range of the 65.Vt "unsigned char" 66type in locales with large character sets is considered obsolete 67and may not be supported in future releases. 68The 69.Fn towlower 70function should be used instead. 71.Sh SEE ALSO 72.Xr ctype 3 , 73.Xr islower 3 , 74.Xr towlower 3 75.Sh STANDARDS 76The 77.Fn tolower 78function conforms to 79.St -isoC . 80