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

# mbrlen(3)

get number of bytes in a character (restartable)

## NAME

**mbrlen** – get number of bytes in a character (restartable)

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

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

*size\_t*\

**mbrlen**(*const char \* restrict s*, *size\_t n*, *mbstate\_t \* restrict ps*);

## DESCRIPTION

The **mbrlen**() function inspects at most *n* bytes pointed to by *s* to determine the number of bytes needed to complete the next multibyte character.

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

It is equivalent to:

```
mbrtowc(NULL, s, n, ps);
```

Except that when *ps* is a NULL pointer, **mbrlen**() uses its own static, internal *mbstate\_t* object to keep track of the shift state.

## RETURN VALUES

The **mbrlen**() 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, **mbrlen**() 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.

## EXAMPLES

A function that calculates the number of characters in a multibyte character string:

```
size_t
nchars(const char *s)
{
	size_t charlen, chars;
	mbstate_t mbs;
	chars = 0;
	memset(&mbs, 0, sizeof(mbs));
	while ((charlen = mbrlen(s, MB_CUR_MAX, &mbs)) != 0 &&
	    charlen != (size_t)-1 && charlen != (size_t)-2) {
		s += charlen;
		chars++;
	}
	return (chars);
}
```

## ERRORS

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

- \[EILSEQ\]

  An invalid multibyte sequence was detected.

- \[EINVAL\]

  The conversion state is invalid.

## SEE ALSO

[mblen(3)](/mblen/3.md), [mbrtowc(3)](/mbrtowc/3.md), [multibyte(3)](/multibyte/3.md)

## STANDARDS

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