MBLEN(3P)                                           POSIX Programmer's Manual                                          MBLEN(3P)



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

NAME
       mblen - get number of bytes in a character

SYNOPSIS
       #include <stdlib.h>

       int mblen(const char *s, size_t n);


DESCRIPTION
       If  s  is  not  a  null  pointer, mblen() shall determine the number of bytes constituting the character pointed to by s.
       Except that the shift state of mbtowc() is not affected, it shall be equivalent to:


              mbtowc((wchar_t *)0, s, n);

       The implementation shall behave as if no function defined in this volume of IEEE Std 1003.1-2001 calls mblen().

       The behavior of this function is affected by the LC_CTYPE category of the current locale. For a state-dependent encoding,
       this  function  shall  be  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.

RETURN VALUE
       If s is a null pointer, mblen() 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, mblen() shall either return 0 (if s points to the null byte),
       or return the number of bytes that constitute the character (if the next n or fewer bytes form  a  valid  character),  or
       return  -1  (if they do not form a valid character)  and may set errno to indicate the error.  In no case shall the value
       returned be greater than n or the value of the {MB_CUR_MAX} macro.

ERRORS
       The mblen() function may fail if:

       EILSEQ Invalid character sequence is detected.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       mbtowc(), mbstowcs(), wctomb(), wcstombs(), the Base Definitions volume of IEEE Std 1003.1-2001, <stdlib.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                     MBLEN(3P)