---
name: "iswblank"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/iswblank"
---

# iswblank(3)

test for whitespace wide character

## NAME

iswblank - test for whitespace wide character

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

```
#include <wctype.h>
```

**int iswblank(wint\_t** *wc***);**

Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

**iswblank**():

```
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
```

## DESCRIPTION

The **iswblank**() function is the wide-character equivalent of the [**isblank**(3)](/isblank/3.md) 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.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **iswblank**() | Thread safety | MT-Safe locale |

## STANDARDS

POSIX.1-2008.

## HISTORY

POSIX.1-2001.

## NOTES

The behavior of **iswblank**() depends on the **LC\_CTYPE** category of the current locale.

## SEE ALSO

[**isblank**(3)](/isblank/3.md), [**iswctype**(3)](/iswctype/3.md)