MBTOWC(3)                  POSIX Programmer's Manual                 MBTOWC(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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 .



IEEE/The Open Group                  2017                            MBTOWC(3)
