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.
For wcsrtombs(): 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 wcsrtombs() function shall convert a sequence of wide characters
from the array indirectly pointed to by src into a sequence of
corresponding characters, beginning in the conversion state described
by the object pointed to by ps. If dst is not a null pointer, the
converted characters shall then be stored into the array pointed to
by dst. 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
* When the next character would exceed the limit of len total bytes
to be stored in the array pointed to by dst (and dst is not a
Each conversion shall take place as if by a call to the wcrtomb()
If dst is not a null pointer, the pointer object pointed to by src
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.
If ps is a null pointer, the wcsrtombs() function shall use its own
internal mbstate_t object, which is initialized at program start-up
to the initial conversion state. Otherwise, the mbstate_t object
pointed to by ps shall be used to completely describe the current
conversion state of the associated character sequence.
The wcsnrtombs() and wcsrtombs() functions need not be thread-safe if
called with a NULL ps argument.
The wcsnrtombs() function shall be equivalent to the wcsrtombs()
function, except that the conversion is limited to the first nwc wide
The wcsrtombs() function shall not change the setting of errno if
The behavior of these functions shall be affected by the LC_CTYPE
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 [EILSEQ] in
errno 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
These functions shall fail if:
EILSEQ A wide-character code does not correspond to a valid
These functions may fail if:
EINVAL ps points to an object that contains an invalid conversion
The following sections are informative.
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 http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
IEEE/The Open Group 2013 WCSRTOMBS(3P)