1.\" $OpenBSD: tolower.3,v 1.14 2017/09/05 03:16:13 schwarze Exp $ 2.\" 3.\" Copyright (c) 1989, 1991 The Regents of the University of California. 4.\" Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org> 5.\" All rights reserved. 6.\" 7.\" This code is derived from software contributed to Berkeley by 8.\" the American National Standards Committee X3, on Information 9.\" Processing Systems. 10.\" 11.\" Redistribution and use in source and binary forms, with or without 12.\" modification, are permitted provided that the following conditions 13.\" are met: 14.\" 1. Redistributions of source code must retain the above copyright 15.\" notice, this list of conditions and the following disclaimer. 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in the 18.\" documentation and/or other materials provided with the distribution. 19.\" 3. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.Dd $Mdocdate: September 5 2017 $ 36.Dt TOLOWER 3 37.Os 38.Sh NAME 39.Nm tolower , 40.Nm tolower_l , 41.Nm _tolower 42.Nd upper case to lower case letter conversion 43.Sh SYNOPSIS 44.In ctype.h 45.Ft int 46.Fn tolower "int c" 47.Ft int 48.Fn tolower_l "int c" "locale_t locale" 49.Ft int 50.Fn _tolower "int c" 51.Sh DESCRIPTION 52The 53.Fn tolower 54and 55.Fn tolower_l 56functions convert an upper-case letter to the corresponding lower-case 57letter. 58The 59.Fn _tolower 60function is identical to 61.Fn tolower 62except that 63.Fa c 64must be an upper-case letter. 65.Pp 66.Ox 67always uses the C locale for these functions, 68ignoring the global locale, the thread-specific locale, and the 69.Fa locale 70argument. 71.Sh RETURN VALUES 72If the argument to the 73.Fn tolower 74or 75.Fn tolower_l 76function is an upper-case letter, the corresponding lower-case letter 77is returned if there is one; otherwise the argument is returned unchanged. 78If the argument to the 79.Fn _tolower 80function is an upper-case letter, the corresponding lower-case letter 81is returned; otherwise the output is undefined. 82.Sh ENVIRONMENT 83On systems supporting non-ASCII single-byte character encodings, 84the results of 85.Fn tolower 86and 87.Fn _tolower 88may depend on the 89.Ev LC_CTYPE 90.Xr locale 1 . 91.Sh SEE ALSO 92.Xr isalnum 3 , 93.Xr isalpha 3 , 94.Xr isascii 3 , 95.Xr isblank 3 , 96.Xr iscntrl 3 , 97.Xr isdigit 3 , 98.Xr isgraph 3 , 99.Xr islower 3 , 100.Xr isprint 3 , 101.Xr ispunct 3 , 102.Xr isspace 3 , 103.Xr isupper 3 , 104.Xr isxdigit 3 , 105.Xr stdio 3 , 106.Xr toascii 3 , 107.Xr toupper 3 , 108.Xr towlower 3 , 109.Xr ascii 7 110.Sh STANDARDS 111The 112.Fn tolower 113and 114.Fn _tolower 115functions conform to 116.St -ansiC , 117and 118.Fn tolower_l 119to 120.St -p1003.1-2008 . 121.Sh HISTORY 122The 123.Fn tolower 124function first appeared in 125.At v7 126and acquired the current semantics in 127.At III , 128where 129.Fn _tolower 130first appeared. 131.Pp 132The 133.Fn tolower_l 134function has been available since 135.Ox 6.2 . 136.Sh CAVEATS 137The argument 138.Fa c 139must be 140.Dv EOF 141or representable as an 142.Li unsigned char ; 143otherwise, the result is undefined. 144