isdigit, isdigit_l—decimal digit predicateSynopsis
#include <ctype.h> int isdigit(int c); #include <ctype.h> int isdigit_l(int c, locale_t locale);
Description
isdigit is a macro which classifies singlebyte charset values by table
lookup. It is a predicate returning non-zero for decimal digits, and 0 for
other characters. It is defined only if c is representable as an
unsigned char or if c is EOF.
isdigit_l is like isdigit 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 isdigit’ or ‘#undef isdigit_l’.
Returns
isdigit, isdigit_l return non-zero if c is a decimal digit
(0–9).
Portability
isdigit is ANSI C.
isdigit_l is POSIX-1.2008.
No supporting OS subroutines are required.