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 character string to a wide-character string
size_t mbstowcs(wchar_t *restrict pwcs, const char *restrict s,
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.1-2017 defers to the ISO C standard.
function shall convert a sequence of characters that begins in the
initial shift state from the array pointed to by
into a sequence of corresponding wide-character codes and shall store
not more than
wide-character codes into the array pointed to by
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
except that the shift state of
is not affected.
No more than
elements shall be modified in the array pointed to by
If copying takes place between objects that overlap, the behavior is
The behavior of this function shall be affected by the
category of the current locale.
is a null pointer,
shall return the length required to convert the entire array regardless
of the value of
but no values are stored.
If an invalid character is encountered,
shall return (size_t
and shall set
to indicate the error.
shall return the number of the array elements modified
(or required if
not including a terminating 0 code, if any. The array shall
not be zero-terminated if the value returned is
function shall fail if:
An invalid character sequence is detected. In the POSIX locale an
error cannot occur since all byte values are valid characters.
The following sections are informative.
The Base Definitions volume of POSIX.1-2017,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
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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