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

# wctomb(3)

convert a wide character to a multibyte sequence

## NAME

wctomb - convert a wide character to a multibyte sequence

## LIBRARY

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

## SYNOPSIS

```
#include <stdlib.h>
```

**int wctomb(char \****s***, wchar\_t** *wc***);**

## DESCRIPTION

If *s* is not NULL, the **wctomb**() function converts the wide character *wc* to its multibyte representation and stores it at the beginning of the character array pointed to by *s*. It updates the shift state, which is stored in a static anonymous variable known only to the **wctomb**() function, and returns the length of said multibyte representation, that is, the number of bytes written at *s*.

At most **MB\_CUR\_MAX** bytes will be written at *s*. The programmer must ensure that there is enough room to store the multibyte sequence at *s*.

If *s* is NULL, the **wctomb**() function resets the shift state, known only to this function, to the initial state, and returns nonzero if the encoding has nontrivial shift state, or zero if the encoding is stateless.

## RETURN VALUE

If *s* is not NULL, the **wctomb**() function returns the number of bytes that have been written to the byte array at *s*. If *wc* can not be represented as a multibyte sequence (according to the current locale), -1 is returned.

If *s* is NULL, the **wctomb**() function returns nonzero if the encoding has nontrivial shift state, or zero if the encoding is stateless.

## ATTRIBUTES

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

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **wctomb**() | Thread safety | MT-Unsafe race |

## VERSIONS

The function [**wcrtomb**(3)](/wcrtomb/3.md) provides a better interface to the same functionality.

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

POSIX.1-2001, C99.

## NOTES

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

## SEE ALSO

[**MB\_CUR\_MAX**(3)](/MB_CUR_MAX/3.md), [**mblen**(3)](/mblen/3.md), [**mbstowcs**(3)](/mbstowcs/3.md), [**mbtowc**(3)](/mbtowc/3.md), [**wcrtomb**(3)](/wcrtomb/3.md), [**wcstombs**(3)](/wcstombs/3.md)