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.
--- get number of bytes in a character (restartable)
size_t mbrlen(const char *restrict s, size_t n,
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.1-2017 defers to the ISO C standard.
is not a null pointer,
shall determine the number of bytes constituting the character pointed
It shall be equivalent to:
mbrtowc(NULL, s, n, ps != NULL ? ps : &internal);
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. The implementation shall behave as
if no function defined in this volume of POSIX.1-2017 calls
The behavior of this function is affected by the
category of the current locale.
function need not be thread-safe if called with a NULL
function shall not change the setting of
function shall return the first of the following that applies:
If the next
or fewer bytes complete the character that corresponds to the null
If the next
or fewer bytes complete a valid character; the value returned shall
be the number of bytes that complete the character.
If the next
bytes contribute to an incomplete but potentially valid character, and
bytes have been processed. When
has at least the value of the
macro, this case can only occur if
points at a sequence of redundant shift sequences (for implementations
with state-dependent encodings).
If an encoding error occurs, in which case the next
or fewer bytes do not contribute to a complete and valid character. In
shall be stored in
and the conversion state is undefined.
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.
function may fail if:
points to an object that contains an invalid conversion state.
The following sections are informative.
The Base Definitions volume of POSIX.1-2017,
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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