This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       None.

       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 http://www.opengroup.org/unix/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
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                        MBRLEN(3POSIX)

       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.

       If  s  is  not  a  null  pointer, mbrlen() shall determine the number of bytes constituting the character
       pointed to by s.  It shall be equivalent to:

           mbstate_t internal;
           mbrtowc(NULL, s, n, ps != NULL ? ps : &internal);

       If ps is a null pointer, the mbrlen() 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 implementation shall behave as if no function defined in this volume of POSIX.1‐2017 calls
       mbrlen().

       The behavior of this function is affected by the LC_CTYPE category of the current locale.

       The mbrlen() function need not be thread-safe if called with a NULL ps argument.

       The mbrlen() function shall not change the setting of errno if successful.

       The mbrlen() function shall fail if:

       EILSEQ An invalid character sequence is detected.  In the POSIX locale an  [EILSEQ]  error  cannot  occur
              since all byte values are valid characters.

       The mbrlen() function may fail if:

       EINVALps points to an object that contains an invalid conversion state.

       Thefollowingsectionsareinformative.

       None.

       None.

       mbrlen — get number of bytes in a character (restartable)

       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.

       None.

       The mbrlen() function shall return the first of the following that applies:

       0           If the next n or fewer bytes complete  the  character  that  corresponds  to  the  null  wide
                   character.

       positive    If  the  next  n  or  fewer bytes complete a valid character; the value returned shall be the
                   number of bytes that complete the character.

       (size_t)-2  If the next n bytes contribute to an incomplete but potentially valid character,  and  all  n
                   bytes have been processed. When n has at least the value of the {MB_CUR_MAX} macro, this case
                   can  only  occur  if s points at a sequence of redundant shift sequences (for implementations
                   with state-dependent encodings).

       (size_t)-1  If an encoding error occurs, in which case the next n or fewer bytes do not contribute  to  a
                   complete  and  valid  character.  In  this  case,  [EILSEQ]  shall be stored in errno and the
                   conversion state is undefined.

mbsinit(), mbrtowc()

       The Base Definitions volume of POSIX.1‐2017, <wchar.h>

       #include <wchar.h>

       size_t mbrlen(const char *restrict s, size_t n,
           mbstate_t *restrict ps);