WCRTOMB(3) Linux Programmer's Manual WCRTOMB(3)
wcrtomb - convert a wide character to a multibyte sequence
size_t wcrtomb(char *s, wchar_t wc, mbstate_t *ps);
The main case for this function is when s is not NULL and wc is not
L'\0'. In this case, the wcrtomb function converts the wide character
wc to its multibyte representation and stores it at the beginning of
the character array pointed to by s. It updates the shift state *ps,
and returns the length of said multibyte representation, i.e. the num-
ber of bytes written at s.
A different case is when s is not NULL but wc is L'\0'. In this case
the wcrtomb function stores at the character array pointed to by s the
shift sequence needed to bring *ps back to the initial state, followed
by a '\0' byte. It updates the shift state *ps (i.e. brings it into the
initial state), and returns the length of the shift sequence plus one,
i.e. the number of bytes written at s.
A third case is when s is NULL. In this case wc is ignored, and the
function effectively returns wcrtomb(buf,L'\0',ps) where buf is an
internal anonymous buffer.
In all of the above cases, if ps is a NULL pointer, a static anonymous
state only known to the wcrtomb function is used instead.
The wcrtomb function returns the number of bytes that have been or
would have been written to the byte array at s. If wc can not be repre-
sented as a multibyte sequence (according to the current locale),
(size_t)(-1) is returned, and errno set to EILSEQ.
ISO/ANSI C, UNIX98
The behaviour of wcrtomb depends on the LC_CTYPE category of the cur-
Passing NULL as ps is not multi-thread safe.
GNU 1999-07-25 WCRTOMB(3)