ISUPPER(3) Library Functions Manual ISUPPER(3)

isupper
upper-case character test

Standard C Library (libc, -lc)

#include <ctype.h>

int
isupper(int c);

The isupper() function tests for any upper-case letter or any of an implementation-defined set of characters for which none of iscntrl(3), isdigit(3), ispunct(3), or isspace(3) is true. In the ``C'' locale, isupper() returns true only for the characters defined as upper-case letters.

The isupper() function returns zero if the character tests false and returns non-zero if the character tests true.

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

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

The argument to isupper() must be EOF or representable as an unsigned char; otherwise, the behavior is undefined. See the CAVEATS section of ctype(3) for more details.
April 17, 2008 NetBSD 9.0