isblank, iswblank, _isblank_l, _iswblank_l

Determines whether an integer represents a blank character.


int isblank(
   int c
int iswblank(
   wint_t c
int _isblank_l(
   int c,
   _locale_t locale
int _iswblank_l(
   wint_t c,
   _locale_t locale


Integer to test.

Locale to use.

Return value

Each of these routines returns nonzero if c is a particular representation of a space or horizontal tab character, or is one of a locale-specific set of characters that are used to separate words within a line of text. isblank returns a nonzero value if c is a space character (0x20) or horizontal tab character (0x09). The result of the test condition for the isblank functions depends on the LC_CTYPE category setting of the locale; for more information, see setlocale, _wsetlocale. The versions of these functions that don't have the _l suffix use the current locale for any locale-dependent behavior; the versions that do have the _l suffix are identical except that they use the locale that's passed in instead. For more information, see Locale.

iswblank returns a nonzero value if c is a wide character that corresponds to a standard space or horizontal tab character.

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

Generic-text routine mappings

TCHAR.H routine _UNICODE and _MBCS not defined _MBCS defined _UNICODE defined
_istblank isblank _ismbcblank iswblank
_istblank_l _isblank_l _ismbcblank_l _iswblank_l


By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.


Routine Required header
isblank <ctype.h>
iswblank <ctype.h> or <wchar.h>
_isblank_l <ctype.h>
_iswblank_l <ctype.h> or <wchar.h>

For more compatibility information, see Compatibility.

See also

Character classification
is, isw routines