TOUPPER(3) Linux Programmer's 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 functions is undefined.
The value returned is that of the converted letter, or c if the conversion was not possi-
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 3.55 of the Linux man-pages project. A description of the
project, and information about reporting bugs, can be found at
GNU 1993-04-04 TOUPPER(3)