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 mbsrtowcs(): 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 mbsrtowcs() function shall convert a sequence of characters,
beginning in the conversion state described by the object pointed to
by ps, from the array indirectly pointed to by src into a sequence of
corresponding wide characters. If dst is not a null pointer, the
converted characters shall be stored into the array pointed to by
dst. Conversion continues up to and including a terminating null
character, which shall also be stored. Conversion shall stop early in
either of the following cases:
* A sequence of bytes is encountered that does not form a valid
* len codes have been stored into the array pointed to by dst (and
dst is not a null pointer).
Each conversion shall take place as if by a call to the mbrtowc()
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 character) or the address just past the
last character converted (if any). If conversion stopped due to
reaching a terminating null character, and if dst is not a null
pointer, the resulting state described shall be the initial
If ps is a null pointer, the mbsrtowcs() 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 mbsnrtowcs() function shall be equivalent to the mbsrtowcs()
function, except that the conversion of characters pointed to by src
is limited to at most nmc bytes (the size of the input buffer).
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 this
volume of POSIX.1‐2008 calls these functions.
The mbsnrtowcs() and mbsrtowcs() functions need not be thread-safe if
called with a NULL ps argument.
The mbsrtowcs() function shall not change the setting of errno if
If the input conversion encounters a sequence of bytes that do not
form a valid character, an encoding error occurs. In this case, these
functions shall store the value of the macro [EILSEQ] in errno and
shall return (size_t)−1; the conversion state is undefined.
Otherwise, these functions shall return the number of characters
successfully converted, not including the terminating null (if any).
These functions shall fail if:
EILSEQ An invalid character sequence is detected.
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 MBSRTOWCS(3P)