iswblank

Iswblank is a wide-character classification function in the C standard library, declared in wchar.h. It tests whether a given wide character is a blank character according to the current locale, returning nonzero if true and zero otherwise. The prototype is int iswblank(wint_t wc). The classification is locale-dependent; the current LC_CTYPE determines which wide characters count as blank. In the default C locale, blank typically includes the space character and the horizontal tab (L' ' and L'\t'). In different locales, additional characters may be classified as blank.

Iswblank is the wide-character counterpart to isblank in <ctype.h> and is related to iswspace, but it is not identical. iswspace checks for a broader set of whitespace characters, including newline and other controls, whereas iswblank focuses on blank spacing in many locales.

Portability and usage: iswblank is part of the C standard since C99 and is available in modern C libraries, including glibc, musl, and MSVC. It requires a valid wide character value of type wint_t, and the result depends on the active locale set by setlocale(LC_CTYPE, ...). Typical usage is to handle input or parsing of wide-character text in a locale-aware way.

See also: setlocale, LC_CTYPE, wchar.h, iswspace, iswalpha.