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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.1‐2008 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.1‐2008 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.
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.1‐2008, <stdlib.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .