3.5 iscntrl, iscntrl_l—control character predicate

Synopsis

#include <ctype.h>
int iscntrl(int c);

#include <ctype.h>
int iscntrl_l(int c, locale_t locale);

Description
iscntrl is a macro which classifies singlebyte charset values by table lookup. It is a predicate returning non-zero for control characters, and 0 for other characters. It is defined only if c is representable as an unsigned char or if c is EOF.

iscntrl_l is like iscntrl but performs the check based on the locale specified by the locale object locale. If locale is LC_GLOBAL_LOCALE or not a valid locale object, the behaviour is undefined.

You can use a compiled subroutine instead of the macro definition by undefining the macro using ‘#undef iscntrl’ or ‘#undef iscntrl_l’.

Returns
iscntrl, iscntrl_l return non-zero if c is a delete character or ordinary control character.

Portability
iscntrl is ANSI C. iscntrl_l is POSIX-1.2008.

No supporting OS subroutines are required.