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

#### NAME

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

#### SYNOPSIS

> ``#include <stdlib.h>
> size_t wcstombs(char *restrict` s`, const wchar_t *restrict` pwcs`,
> 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 wcstombs() function shall convert the sequence of wide-character codes that are in the array pointed to by pwcs into a sequence of characters that begins in the initial shift state and store these characters into the array pointed to by s, stopping if a character would exceed the limit of n total bytes or if a null byte is stored. Each wide-character code shall be converted as if by a call to wctomb(), except that the shift state of wctomb() shall not be affected.

> The behavior of this function shall be affected by the LC_CTYPE category of the current locale.

> No more than n bytes shall be modified in the array pointed to by s. If copying takes place between objects that overlap, the behavior is undefined. [CX] If s is a null pointer, wcstombs() shall return the length required to convert the entire array regardless of the value of n, but no values are stored.

#### RETURN VALUE

> If a wide-character code is encountered that does not correspond to a valid character (of one or more bytes each), wcstombs() shall return (size_t)-1. Otherwise, wcstombs() shall return the number of bytes stored in the character array, not including any terminating null byte. The array shall not be null-terminated if the value returned is n.

#### ERRORS

> The wcstombs() function shall fail if:

> [EILSEQ]
>   [CX] A wide-character code does not correspond to a valid character.

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> None.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> mblen, mbtowc, mbstowcs, wctomb

> XBD <stdlib.h>

#### CHANGE HISTORY

> First released in Issue 4. Derived from the ISO C standard.

#### Issue 6

> The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

> - The DESCRIPTION states the effect of when s is a null pointer.

> - The [EILSEQ] error condition is added.

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

#### Issue 7

> Austin Group Interpretations 1003.1-2001 #156 and #170 are applied.

> POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0726 [109] is applied.

End of informative text.

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