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                                       WCRTOMB(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 a null pointer, the wcrtomb() function shall be equivalent to the call:

           wcrtomb(buf, L'\0', ps)

       where buf is an internal buffer.

       If  s  is  not  a  null  pointer,  the  wcrtomb()  function shall determine the number of bytes needed to
       represent the character that corresponds  to  the  wide  character  given  by  wc  (including  any  shift
       sequences),  and  store the resulting bytes in the array whose first element is pointed to by s.  At most
       {MB_CUR_MAX} bytes are stored. If wc is a null wide character, a null byte shall be stored,  preceded  by
       any  shift sequence needed to restore the initial shift state. The resulting state described shall be the
       initial conversion state.

       If ps is a null pointer, the wcrtomb() 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
       wcrtomb().

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

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

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

       The wcrtomb() function shall fail if:

       EILSEQ An invalid wide-character code is detected.

       The wcrtomb() function may fail if:

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

       Thefollowingsectionsareinformative.

       None.

       None.

       wcrtomb — convert a wide-character code to 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 wcrtomb() function shall return the number of bytes stored in the array object (including  any  shift
       sequences).  When  wc  is  not  a  valid wide character, an encoding error shall occur. In this case, the
       function shall store the value of the macro [EILSEQ] in errno and shall return (size_t)-1; the conversion
       state shall be undefined.

mbsinit(), wcsrtombs()

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

       #include <wchar.h>

       size_t wcrtomb(char *restrict s, wchar_t wc, mbstate_t *restrict ps);