isdigit, iswdigit, _isdigit_l, _iswdigit_l

Determines whether an integer represents a decimal-digit character.

Syntax

int isdigit(
   int c
);
int iswdigit(
   wint_t c
);
int _isdigit_l(
   int c,
   _locale_t locale
);
int _iswdigit_l(
   wint_t c,
   _locale_t locale
);

Parameters

c
Integer to test.

locale
The locale to use.

Return Value

Each of these routines returns nonzero if c is a particular representation of a decimal-digit character. isdigit returns a nonzero value if c is a decimal digit (0 - 9). iswdigit returns a nonzero value if c is a wide character that corresponds to a decimal-digit character. Each of these routines returns 0 if c does not satisfy the test condition.

The versions of these functions that have the _l suffix use the locale that's passed in instead of the current locale for their locale-dependent behavior. For more information, see Locale.

The behavior of isdigit and _isdigit_l is undefined if c is not EOF or in the range 0 through 0xFF, inclusive. When a debug CRT library is used and c is not one of these values, the functions raise an assertion.

Generic-Text Routine Mappings

TCHAR.H routine _UNICODE & _MBCS not defined _MBCS defined _UNICODE defined
_istdigit isdigit _ismbcdigit iswdigit
_istdigit_l _isdigit_l _ismbcdigit_l _iswdigit_l

Requirements

Routine Required header
isdigit <ctype.h>
iswdigit <ctype.h> or <wchar.h>
_isdigit_l <ctype.h>
_iswdigit_l <ctype.h> or <wchar.h>

For additional compatibility information, see Compatibility.

See also

Character Classification
Locale
is, isw Routines