iscntrl---control character predicate#include <ctype.h> int iscntrl(int c);Description
iscntrl is a macro which classifies ASCII integer values by table
lookup. It is a predicate returning non-zero for control characters, and 0
for other characters. It is defined only when isascii(c) is
true or c is EOF.
You can use a compiled subroutine instead of the macro definition by
undefining the macro using `#undef iscntrl'.
Returns
iscntrl returns non-zero if c is a delete character or ordinary
control character (0x7F or 0x00--0x1F).
Portability
iscntrl is ANSI C.
No supporting OS subroutines are required.