---
name: "mbrtowc"
section: "3"
platform: "macos"
package: "Libc"
version: "1752.120.2"
release: "macOS 26.5"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/mbrtowc"
---

# mbrtowc(3)

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

## NAME

**mbrtowc**, **mbrtowc\_l** – convert a character to a wide-character code (restartable)

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

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

*size\_t*\

**mbrtowc**(*wchar\_t \*restrict pwc*, *const char \*restrict s*, *size\_t n*, *mbstate\_t \*restrict ps*);

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

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

*size\_t*\

**mbrtowc\_l**(*wchar\_t \*restrict pwc*, *const char \*restrict s*, *size\_t n*, *mbstate\_t \*restrict ps*, *locale\_t loc*);

## DESCRIPTION

The **mbrtowc**() function inspects at most *n* bytes, pointed to by *s*, to determine the number of bytes needed to complete the next multibyte character. If a character can be completed, and *pwc* is not NULL, the wide character which is represented by *s* is stored in the *wchar\_t* it points to.

If *s* is NULL, **mbrtowc**() behaves as if *pwc* were NULL, *s* were an empty string (""), and *n* were 1.

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

While the **mbrtowc**() function uses the current locale, the **mbrtowc\_l**() function may be passed a locale directly. See [xlocale(3)](/xlocale/3.md) for more information.

## RETURN VALUES

The **mbrtowc**() functions returns:

- 0

  The next *n* or fewer bytes represent the null wide character (L'\\0').

- \>0

  The next *n* or fewer bytes represent a valid character, **mbrtowc**() returns the number of bytes used to complete the multibyte character.

- (*size\_t*)-2

  The next *n* contribute to, but do not complete, a valid multibyte character sequence, and all *n* bytes have been processed.

- (*size\_t*)-1

  An encoding error has occurred. The next *n* or fewer bytes do not contribute to a valid multibyte character.

## ERRORS

The **mbrtowc**() function will fail if:

- \[EILSEQ\]

  An invalid multibyte sequence was detected.

- \[EINVAL\]

  The conversion state is invalid.

## SEE ALSO

[mbtowc(3)](/mbtowc/3.md), [multibyte(3)](/multibyte/3.md), [setlocale(3)](/setlocale/3.md), [wcrtomb(3)](/wcrtomb/3.md), [xlocale(3)](/xlocale/3.md)

## STANDARDS

The **mbrtowc**() function conforms to ISO/IEC 9899:1999 (“ISO C99”).