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Manual Reference Pages  - TOUPPER (3)

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toupper, tolower - convert letter to upper or lower case

CONTENTS

Synopsis
Description
Bugs

#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 behaviour of these functions is undefined.

The value returned is that of the converted letter, or c if the conversion was not possible.

ANSI C, BSD 4.3

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), locale(7)

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