toupper (3)
NAME
toupper, tolower - convert letter to upper or lower caseSYNOPSIS
#include <ctype.h> int toupper(int c);
int tolower(int c);
DESCRIPTION
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.
RETURN VALUE
The value returned is that of the converted letter, or c if the conversion was not possible.CONFORMING TO
C89, C99, 4.3BSD.BUGS
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.
SEE ALSO
isalpha(3), setlocale(3), towlower(3), towupper(3), locale(7)COLOPHON
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