---
name: "iswlower"
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/iswlower"
---

# iswlower(3)

test for lowercase wide character

## NAME

iswlower - test for lowercase wide character

## LIBRARY

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

## SYNOPSIS

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

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

## DESCRIPTION

The **iswlower**() function is the wide-character equivalent of the [**islower**(3)](/islower/3.md) function. It tests whether *wc* is a wide character belonging to the wide-character class "lower".

The wide-character class "lower" is a subclass of the wide-character class "alpha", and therefore also a subclass of the wide-character class "alnum", of the wide-character class "graph" and of the wide-character class "print".

Being a subclass of the wide-character class "print", the wide-character class "lower" is disjoint from the wide-character class "cntrl".

Being a subclass of the wide-character class "graph", the wide-character class "lower" is disjoint from the wide-character class "space" and its subclass "blank".

Being a subclass of the wide-character class "alnum", the wide-character class "lower" is disjoint from the wide-character class "punct".

Being a subclass of the wide-character class "alpha", the wide-character class "lower" is disjoint from the wide-character class "digit".

The wide-character class "lower" contains at least those characters *wc* which are equal to *towlower(wc)* and different from *towupper(wc)*.

The wide-character class "lower" always contains at least the letters 'a' to 'z'.

## RETURN VALUE

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

## ATTRIBUTES

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

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

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

POSIX.1-2001, C99.

## NOTES

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

This function is not very appropriate for dealing with Unicode characters, because Unicode knows about three cases: upper, lower, and title case.

## SEE ALSO

[**islower**(3)](/islower/3.md), [**iswctype**(3)](/iswctype/3.md), [**towlower**(3)](/towlower/3.md)