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

       mblen — get number of bytes in a character

SYNOPSIS

       #include <stdlib.h>

       int mblen(const char *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, 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 POSIX.1‐2017
       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.

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

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 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

       mbtowc(), 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 .