Copyright (c) 1989, 1991 The Regents of the University of California.
Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org>
All rights reserved.
This code is derived from software contributed to Berkeley by
the American National Standards Committee X3, on Information
Processing Systems.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. Neither the name of the University nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
.Dd $Mdocdate: September 5 2017 $ .Dt TOLOWER 3 .Os .Sh NAME .Nm tolower , .Nm tolower_l , .Nm _tolower .Nd upper case to lower case letter conversion .Sh SYNOPSIS n ctype.h .Ft int .Fn tolower "int c" .Ft int .Fn tolower_l "int c" "locale_t locale" .Ft int .Fn _tolower "int c" .Sh DESCRIPTION The .Fn tolower and .Fn tolower_l functions convert an upper-case letter to the corresponding lower-case letter. The .Fn _tolower function is identical to .Fn tolower except that .Fa c must be an upper-case letter.
p .Ox always uses the C locale for these functions, ignoring the global locale, the thread-specific locale, and the .Fa locale argument. .Sh RETURN VALUES If the argument to the .Fn tolower or .Fn tolower_l function is an upper-case letter, the corresponding lower-case letter is returned if there is one; otherwise the argument is returned unchanged. If the argument to the .Fn _tolower function is an upper-case letter, the corresponding lower-case letter is returned; otherwise the output is undefined. .Sh ENVIRONMENT On systems supporting non-ASCII single-byte character encodings, the results of .Fn tolower and .Fn _tolower may depend on the .Ev LC_CTYPE .Xr locale 1 . .Sh SEE ALSO .Xr isalnum 3 , .Xr isalpha 3 , .Xr isascii 3 , .Xr isblank 3 , .Xr iscntrl 3 , .Xr isdigit 3 , .Xr isgraph 3 , .Xr islower 3 , .Xr isprint 3 , .Xr ispunct 3 , .Xr isspace 3 , .Xr isupper 3 , .Xr isxdigit 3 , .Xr stdio 3 , .Xr toascii 3 , .Xr toupper 3 , .Xr towlower 3 , .Xr ascii 7 .Sh STANDARDS The .Fn tolower and .Fn _tolower functions conform to .St -ansiC , and .Fn tolower_l to .St -p1003.1-2008 . .Sh HISTORY The .Fn tolower function first appeared in .At v7 and acquired the current semantics in .At III , where .Fn _tolower first appeared.
p The .Fn tolower_l function has been available since .Ox 6.2 . .Sh CAVEATS The argument .Fa c must be .Dv EOF or representable as an .Vt unsigned char ; otherwise, the result is undefined.