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TOUPPER(3) Library Functions Manual TOUPPER(3)

toupper, _toupperlower case to upper case letter conversion

#include <ctype.h>

int
toupper(int c);

int
_toupper(int c);

The () function converts a lower-case letter to the corresponding upper-case letter. The () function is identical to toupper() except that c must be a lower-case letter.

If the argument to the toupper() function is a lower-case letter, the corresponding upper-case letter is returned if there is one; otherwise the argument is returned unchanged. If the argument to the _toupper() function is a lower-case letter, the corresponding upper-case letter is returned; otherwise the output is undefined.

isalnum(3), isalpha(3), isascii(3), isblank(3), iscntrl(3), isdigit(3), isgraph(3), islower(3), isprint(3), ispunct(3), isspace(3), isupper(3), isxdigit(3), stdio(3), toascii(3), tolower(3), ascii(7)

The toupper() function conforms to ANSI X3.159-1989 (“ANSI C89”).

The argument to toupper must be EOF or representable as an unsigned char; otherwise, the result is undefined.

June 5, 2013 OpenBSD-5.9