| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | BUGS | SEE ALSO | COLOPHON | The Linux Programming Interface |
TOUPPER(3) Linux Programmer's Manual TOUPPER(3)
toupper, tolower - convert letter to upper or lower case
#include <ctype.h>
int toupper(int c);
int tolower(int c);
toupper() converts the letter c to upper case, if possible.
tolower() converts the letter c to lower case, if possible.
If c is not an unsigned char value, or EOF, the behavior of these functions is
undefined.
The value returned is that of the converted letter, or c if the conversion was
not possible.
C89, C99, 4.3BSD.
The details of what constitutes an uppercase or lowercase letter depend on the
current locale. For example, the default "C" locale does not know about
umlauts, so no conversion is done for them.
In some non-English locales, there are lowercase letters with no corresponding
uppercase equivalent; the German sharp s is one example.
isalpha(3), setlocale(3), towlower(3), towupper(3), locale(7)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 1993-04-04 TOUPPER(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface