iswblank - Man Page

test for whitespace wide character


#include <wctype.h>

int iswblank(wint_t wc);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):


    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L


The iswblank() function is the wide-character equivalent of the isblank(3) function. It tests whether wc is a wide character belonging to the wide-character class "blank".

The wide-character class "blank" is a subclass of the wide-character class "space".

Being a subclass of the wide-character class "space", the wide-character class "blank" is disjoint from the wide-character class "graph" and therefore also disjoint from its subclasses "alnum", "alpha", "upper", "lower", "digit", "xdigit", "punct".

The wide-character class "blank" always contains at least the space character and the control character '\t'.

Return Value

The iswblank() function returns nonzero if wc is a wide character belonging to the wide-character class "blank". Otherwise, it returns zero.


For an explanation of the terms used in this section, see attributes(7).

iswblank()Thread safetyMT-Safe locale

Conforming to

POSIX.1-2001, POSIX.1-2008.


The behavior of iswblank() depends on the LC_CTYPE category of the current locale.

See Also

isblank(3), iswctype(3)


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Referenced By

isalpha(3), iswctype(3).

2021-03-22 GNU Linux Programmer's Manual