mblen(3p) — Linux manual page


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

PROLOG         top

       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         top

       mblen — get number of bytes in a character

SYNOPSIS         top

       #include <stdlib.h>

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

DESCRIPTION         top

       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         top

       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         top

       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         top




RATIONALE         top




SEE ALSO         top

       mbtowc(3p), mbstowcs(3p), wctomb(3p), wcstombs(3p)

       The Base Definitions volume of POSIX.1‐2017, stdlib.h(0p)

COPYRIGHT         top

       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(3P)

Pages that refer to this page: ctype.h(0p)stdlib.h(0p)mbstowcs(3p)mbtowc(3p)setlocale(3p)wcstombs(3p)wctomb(3p)