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



PPRROOLLOOGG
       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.

NNAAMMEE
       mblen -- get number of bytes in a character

SSYYNNOOPPSSIISS
       #include <stdlib.h>

       int mblen(const char *_s, size_t _n);

DDEESSCCRRIIPPTTIIOONN
       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, _m_b_l_e_n() shall determine the number of bytes
       constituting the character pointed to by _s.  Except that the shift
       state of _m_b_t_o_w_c() 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 _m_b_l_e_n().

       The behavior of this function is affected by the _L_C___C_T_Y_P_E 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 _L_C___C_T_Y_P_E category causes the shift state of
       this function to be unspecified.

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

RREETTUURRNN VVAALLUUEE
       If _s is a null pointer, _m_b_l_e_n() 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, _m_b_l_e_n() 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 _e_r_r_n_o to indicate the error.  In no case shall the value
       returned be greater than _n or the value of the {MB_CUR_MAX} macro.

EERRRROORRSS
       The _m_b_l_e_n() function may fail if:

       EEIILLSSEEQQ An invalid character sequence is detected. In the POSIX locale
              an [[EEIILLSSEEQQ]] error cannot occur since all byte values are valid
              characters.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       None.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _m_b_t_o_w_c(), _m_b_s_t_o_w_c_s(), _w_c_t_o_m_b(), _w_c_s_t_o_m_b_s()

       The Base Definitions volume of POSIX.1-2017, <<ssttddlliibb..hh>>

CCOOPPYYRRIIGGHHTT
       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                             MBLEN(3)
