---
name: "c16rtomb"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/c16rtomb"
---

# c16rtomb(3)

convert a wide-character code to a character (restartable)

## NAME

**wcrtomb**, **c16rtomb**, **c32rtomb** – convert a wide-character code to a character (restartable)

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<wchar.h\>**

*size\_t*\

**wcrtomb**(*char \* restrict s*, *wchar\_t c*, *mbstate\_t \* restrict ps*);

**#include \<uchar.h\>**

*size\_t*\

**c16rtomb**(*char \* restrict s*, *char16\_t c*, *mbstate\_t \* restrict ps*);

*size\_t*\

**c32rtomb**(*char \* restrict s*, *char32\_t c*, *mbstate\_t \* restrict ps*);

## DESCRIPTION

The **wcrtomb**(), **c16rtomb**() and **c32rtomb**() functions store a multibyte sequence representing the wide character *c*, including any necessary shift sequences, to the character array *s*, storing a maximum of MB\_CUR\_MAX bytes.

If *s* is NULL, these functions behave as if *s* pointed to an internal buffer and *c* was a null wide character (L'\\0').

The *mbstate\_t* argument, *ps*, is used to keep track of the shift state. If it is NULL, these functions use an internal, static *mbstate\_t* object, which is initialized to the initial conversion state at program startup.

As certain multibyte characters may only be represented by a series of 16-bit characters, the **c16rtomb**() may need to invoked multiple times before a multibyte sequence is returned.

## RETURN VALUES

These functions return the length (in bytes) of the multibyte sequence needed to represent *c*, or (*size\_t*)-1 if *c* is not a valid wide character code.

## ERRORS

The **wcrtomb**(), **c16rtomb**() and **c32rtomb**() functions will fail if:

- \[EILSEQ\]

  An invalid wide character code was specified.

- \[EINVAL\]

  The conversion state is invalid.

## SEE ALSO

[mbrtowc(3)](/mbrtowc/3.md), [multibyte(3)](/multibyte/3.md), [setlocale(3)](/setlocale/3.md), [wctomb(3)](/wctomb/3.md)

## STANDARDS

The **wcrtomb**(), **c16rtomb**() and **c32rtomb**() functions conform to ISO/IEC 9899:2011 (“ISO C11”).