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.\" $OpenBSD: islower.3,v 1.13 2017/09/05 03:16:13 schwarze Exp $
.\"
.\" Copyright (c) 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 ISLOWER 3
.Os
.Sh NAME
.Nm islower ,
.Nm islower_l
.Nd lower-case single-byte character test
.Sh SYNOPSIS
.In ctype.h
.Ft int
.Fn islower "int c"
.Ft int
.Fn islower_l "int c" "locale_t locale"
.Sh DESCRIPTION
The
.Fn islower
and
.Fn islower_l
functions test whether
.Fa c
represents a lower-case letter.
.Pp
In the C locale, the complete list of lower-case letters is a\(enz.
.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
These functions return zero if the character tests false or
non-zero if the character tests true.
.Sh ENVIRONMENT
On systems supporting non-ASCII single-byte character encodings,
these functions may return non-zero for additional characters,
and the results of
.Fn islower
may depend on the
.Ev LC_CTYPE
.Xr locale 1 ,
but they never return non-zero for any character for which
.Xr iscntrl 3 ,
.Xr isdigit 3 ,
.Xr ispunct 3 ,
or
.Xr isspace 3
is true.
.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 isprint 3 ,
.Xr ispunct 3 ,
.Xr isspace 3 ,
.Xr isupper 3 ,
.Xr iswlower 3 ,
.Xr isxdigit 3 ,
.Xr stdio 3 ,
.Xr toascii 3 ,
.Xr tolower 3 ,
.Xr toupper 3 ,
.Xr ascii 7
.Sh STANDARDS
The
.Fn islower
function conforms to
.St -ansiC ,
and
.Fn islower_l
to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn islower
function first appeared in
.At v7 ,
AND
.Fn islower_l
has been available since
.Ox 6.2 .
.Sh CAVEATS
The argument
.Fa c
must be
.Dv EOF
or representable as an
.Li unsigned char ;
otherwise, the result is undefined.
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