PROLOG

       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.

NAME

       mbtowc — convert a character to a wide-character code

SYNOPSIS

       #include <stdlib.h>

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

DESCRIPTION

       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.

RETURN VALUE

       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.

ERRORS

       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.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

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

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

COPYRIGHT

       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 .