The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

> mbstowcs - convert a character string to a wide-character string

#### SYNOPSIS

> ``#include <stdlib.h>
> size_t mbstowcs(wchar_t *restrict` pwcs`, const char *restrict` s`,
> size_t` n`);
> ``

#### DESCRIPTION

> [CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.

> The mbstowcs() function shall convert a sequence of characters that begins in the initial shift state from the array pointed to by s into a sequence of corresponding wide-character codes and shall store not more than n wide-character codes into the array pointed to by pwcs. No characters that follow a null byte (which is converted into a wide-character code with value 0) shall be examined or converted. Each character shall be converted as if by a call to mbtowc(), except that the shift state of mbtowc() is not affected.

> No more than n elements shall be modified in the array pointed to by pwcs. If copying takes place between objects that overlap, the behavior is undefined.

> The behavior of this function shall be affected by the LC_CTYPE category of the current locale. [XSI] If pwcs is a null pointer, mbstowcs() shall return the length required to convert the entire array regardless of the value of n, but no values are stored.

#### RETURN VALUE

> If an invalid character is encountered, mbstowcs() shall return (size_t)-1 [CX] and shall set errno to indicate the error.

> Otherwise, mbstowcs() shall return the number of the array elements modified [XSI] (or required if pwcs is null), not including a terminating 0 code, if any. The array shall not be zero-terminated if the value returned is n.

#### ERRORS

> The mbstowcs() function shall fail if:

> [EILSEQ]
>   [CX] An invalid character sequence is detected. In the POSIX locale an [EILSEQ] error cannot occur since all byte values are valid characters.

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> None.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> mblen, mbtowc, wctomb, wcstombs

> XBD <stdlib.h>

#### CHANGE HISTORY

> First released in Issue 4. Aligned with the ISO C standard.

#### Issue 6

> The mbstowcs() prototype is updated for alignment with the ISO/IEC 9899:1999 standard.

> Extensions beyond the ISO C standard are marked.

#### Issue 7

> Austin Group Interpretation 1003.1-2001 #170 is applied.

> POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0371 [195] is applied.

> POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0208 [663,674] is applied.

End of informative text.

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