isdigit, iswdigit, _isdigit_l, _iswdigit_l
Determines whether an integer represents a decimal-digit character.
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 );
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.