.\" (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
.\"
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.\" Modified Sat Jul 24 17:45:39 1993 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2000-02-13 by Nicolás Lichtmaier <nick@debian.org>
.TH TOUPPER 3  "April 4, 1993" "GNU" "Linux Programmer's Manual"
.SH NAME
toupper, tolower \- convert letter to upper or lower case
.SH SYNOPSIS
.nf
.B #include <ctype.h>
.sp
.BI "int toupper (int " "c" ");"
.nl
.BI "int tolower (int " "c" ");"
.fi
.SH DESCRIPTION
.B toupper()
converts the letter
.I c
to upper case, if possible.
.PP
.B tolower()
converts the letter
.I c
to lower case, if possible.
.PP
If
.I c
is not an unsigned char value, or EOF, the behaviour of these functions
is undefined.
.SH "RETURN VALUE"
The value returned is that of the converted letter, or
.I c
if the conversion was not possible.
.SH "CONFORMING TO"
ANSI C, BSD 4.3
.SH "BUGS"
The details of what constitutes an uppercase or lowercase letter depend
on the current locale.  For example, the default
.B """C"""
locale does not know about umlauts, so no conversion is done for them.
.PP
In some non - English locales, there are lowercase letters with no
corresponding uppercase equivalent; the German sharp s is one
example.
.SH "SEE ALSO"
.BR isalpha "(3), " setlocale "(3), " locale (7)