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                                        MBTOWC(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, mbtowc() shall determine the number of bytes that constitute the character
       pointed to by s.  It shall then determine the wide-character code for the  value  of  type  wchar_t  that
       corresponds  to  that  character. (The value of the wide-character code corresponding to the null byte is
       0.) If the character is valid and pwc is not a null pointer, mbtowc() shall store the wide-character code
       in the object pointed to by pwc.

       The behavior of this function is affected by the LC_CTYPE category of the current locale.  For  a  state-
       dependent  encoding,  this  function  is  placed into its initial state by a call for which its character
       pointer argument, s, is a null pointer. Subsequent calls with s as other than a null pointer shall  cause
       the  internal  state  of  the  function to be altered as necessary. A call with s as a null pointer shall
       cause this function to return a non-zero value if encodings have state dependency, and  0  otherwise.  If
       the  implementation  employs  special  bytes  to  change  the  shift state, these bytes shall not produce
       separate wide-character codes, but shall be grouped with an adjacent  character.  Changing  the  LC_CTYPE
       category  causes the shift state of this function to be unspecified. At most n bytes of the array pointed
       to by s shall be examined.

       The implementation shall behave as if no function defined in this volume of POSIX.1‐2017 calls mbtowc().

       The mbtowc() function need not be thread-safe.

       The mbtowc() 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.

       Thefollowingsectionsareinformative.

       None.

       None.

       mbtowc — convert a character to a wide-character code

       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.

       If s is a  null  pointer,  mbtowc()  shall  return  a  non-zero  or  0  value,  if  character  encodings,
       respectively,  do  or  do  not have state-dependent encodings. If s is not a null pointer, mbtowc() shall
       either return 0 (if s points to the null byte), or  return  the  number  of  bytes  that  constitute  the
       converted  character  (if  the  next n or fewer bytes form a valid character), or return -1 and shall set
       errno to indicate the error (if they do not form a valid character).

       In no case shall the value returned be greater than n or the value of the {MB_CUR_MAX} macro.

mblen(), mbstowcs(), wctomb(), wcstombs()

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

       #include <stdlib.h>

       int mbtowc(wchar_t *restrict pwc, const char *restrict s, size_t n);