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isxdigit
[hexadecimal digit predicate]

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

DESCRIPTION
isxdigit is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for hexadecimal digits, 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 isxdigit.

RETURNS
isxdigit returns non-zero if c is a hexadecimal digit (0–9, a–f, or A–F).

COMPLIANCE
isxdigit is ANSI C.

No supporting OS subroutines are required.