TOUPPER(3) Linux Programmers Manual TOUPPER(3)
toupper, tolower - convert letter to upper or lower case
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 func
tions is undefined.
The value returned is that of the converted letter, or c if the conver
sion 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 corre
sponding 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 3.05 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)