# mbrlen

## 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



           mbrlen — get number of bytes in a character (restartable)
    


## SYNOPSIS



           #include <wchar.h>
    
           size_t mbrlen(const char *restrict _s_ , size_t _n_ ,
               mbstate_t *restrict _ps_);
    


## 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, _mbrlen_() shall determine the number of
           bytes constituting the character pointed to by _s_.  It shall be
           equivalent to:
    
               mbstate_t internal;
               mbrtowc(NULL, s, n, ps != NULL ? ps : &internal);
    
           If _ps_ is a null pointer, the _mbrlen_() function shall use its own
           internal **mbstate_t** object, which is initialized at program start-
           up to the initial conversion state. Otherwise, the **mbstate_t**
           object pointed to by _ps_ shall be used to completely describe the
           current conversion state of the associated character sequence. The
           implementation shall behave as if no function defined in this
           volume of POSIX.1‐2017 calls _mbrlen_().
    
           The behavior of this function is affected by the _LC_CTYPE_ category
           of the current locale.
    
           The _mbrlen_() function need not be thread-safe if called with a
           NULL _ps_ argument.
    
           The _mbrlen_() function shall not change the setting of _errno_ if
           successful.
    


## RETURN VALUE



           The _mbrlen_() function shall return the first of the following that
           applies:
    
           0           If the next _n_ or fewer bytes complete the character
                       that corresponds to the null wide character.
    
           _positive_    If the next _n_ or fewer bytes complete a valid
                       character; the value returned shall be the number of
                       bytes that complete the character.
    
           (**size_t**)-2  If the next _n_ bytes contribute to an incomplete but
                       potentially valid character, and all _n_ bytes have been
                       processed. When _n_ has at least the value of the
                       {MB_CUR_MAX} macro, this case can only occur if _s_
                       points at a sequence of redundant shift sequences (for
                       implementations with state-dependent encodings).
    
           (**size_t**)-1  If an encoding error occurs, in which case the next _n_
                       or fewer bytes do not contribute to a complete and
                       valid character. In this case, **[EILSEQ]** shall be
                       stored in _errno_ and the conversion state is undefined.
    


## ERRORS



           The _mbrlen_() function shall 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 _mbrlen_() function may fail if:
    
           **EINVAL** _ps_ points to an object that contains an invalid conversion
                  state.
    
           _The following sections are informative._
    


## EXAMPLES



           None.
    


## APPLICATION USAGE



           None.
    


## RATIONALE



           None.
    


## FUTURE DIRECTIONS



           None.
    


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