Section: POSIX Programmer's Manual (3P)
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
--- convert a wide-character string to a character string (restartable)
size_t wcsnrtombs(char *restrict dst, const wchar_t **restrict src,
size_t nwc, size_t len, mbstate_t *restrict ps);
size_t wcsrtombs(char *restrict dst, const wchar_t **restrict src,
size_t len, mbstate_t *restrict ps);
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.
function shall convert a sequence of wide characters from the array
indirectly pointed to by
into a sequence of corresponding characters, beginning in the
conversion state described by the object pointed to by
is not a null pointer, the converted characters shall then be
stored into the array pointed to by
Conversion continues up to and including a terminating null wide
character, which shall also be stored. Conversion shall stop
earlier in the following cases:
When a code is reached that does not correspond to a valid character
When the next character would exceed the limit of
total bytes to be stored in the array pointed to by
is not a null pointer)
Each conversion shall take place as if by a call to the
is not a null pointer, the pointer object pointed to by
shall be assigned either a null pointer (if conversion stopped due to
reaching a terminating null wide character) or the address just past
the last wide character converted (if any). If conversion stopped due
to reaching a terminating null wide character, the resulting state
described shall be the initial conversion state.
is a null pointer, the
function shall use its own internal
object, which is initialized at program start-up to the initial
conversion state. Otherwise, the
object pointed to by
shall be used to completely describe the current conversion state of
the associated character sequence.
functions need not be thread-safe if called with a NULL
function shall be equivalent to the
function, except that the conversion is limited to the first
function shall not change the setting of
The behavior of these functions shall be affected by the
category of the current locale.
The implementation shall behave as if no function defined in System Interfaces volume of POSIX.1-2008
calls these functions.
If conversion stops because a code is reached that does not correspond
to a valid character, an encoding error occurs. In this case, these
functions shall store the value of the macro
and return (size_t
)-1; the conversion state is undefined.
Otherwise, these functions shall return the number of bytes in the
resulting character sequence, not including the terminating null (if any).
These functions shall fail if:
A wide-character code does not correspond to a valid character.
These functions may fail if:
points to an object that contains an invalid conversion state.
The following sections are informative.
The Base Definitions volume of POSIX.1-2008,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
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