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 December 19, 2022 36.Dt TOLOWER 3 37.Os 38.Sh NAME 39.Nm tolower , 40.Nm tolower_l 41.Nd upper case to lower case letter conversion 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In ctype.h 46.Ft int 47.Fn tolower "int c" 48.Ft int 49.Fn tolower_l "int c" "locale_t loc" 50.Sh DESCRIPTION 51The 52.Fn tolower 53and 54.Fn tolower_l 55functions convert an upper-case letter to the corresponding lower-case 56letter. 57The argument must be representable as an 58.Vt "unsigned char" 59or the value of 60.Dv EOF . 61.Pp 62The 63.Fn tolower_l 64function takes an explicit locale argument, whereas the 65.Fn tolower 66function uses the current global or per-thread locale. 67.Sh RETURN VALUES 68If the argument is an upper-case letter, the 69.Fn tolower 70and 71.Fn tolower_l 72functions return the corresponding lower-case letter if there is 73one; otherwise, the argument is returned unchanged. 74.Sh COMPATIBILITY 75The 76.Bx 4.4 77extension of accepting arguments outside of the range of the 78.Vt "unsigned char" 79type in locales with large character sets is considered obsolete 80and may not be supported in future releases. 81The 82.Fn towlower 83or 84.Fn towlower_l 85function should be used instead. 86.Sh SEE ALSO 87.Xr ctype 3 , 88.Xr ctype_l 3 , 89.Xr islower 3 , 90.Xr islower_l 3 , 91.Xr towlower 3 , 92.Xr towlower_l 3 , 93.Xr xlocale 3 94.Sh STANDARDS 95The 96.Fn tolower 97function conforms to 98.St -isoC . 99