wcrtomb(3) Library Functions Manual wcrtomb(3)
NAME
wcrtomb - convert a wide character to a multibyte sequence
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <wchar.h>
size_t wcrtomb(char *restrict s, wchar_t wc, mbstate_t *restrict ps);
DESCRIPTION
The main case for this function is when s is not NULL and wc is not a
null wide character (L'\0'). In this case, the wcrtomb() function con-
verts 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 represen-
tation, that is, the number of bytes written at s.
A different case is when s is not NULL, but wc is a null wide character
(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, that is, 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 NULL, a static anonymous state known
only to the wcrtomb() function is used instead.
RETURN VALUE
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.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌─────────────────────────┬───────────────┬────────────────────────────┐
│ Interface │ Attribute │ Value │
├─────────────────────────┼───────────────┼────────────────────────────┤
│ wcrtomb() │ Thread safety │ MT-Unsafe race:wcrtomb/!ps │
└─────────────────────────┴───────────────┴────────────────────────────┘
STANDARDS
C11, POSIX.1-2008.
HISTORY
POSIX.1-2001, C99.
NOTES
The behavior of wcrtomb() depends on the LC_CTYPE category of the cur-
rent locale.
Passing NULL as ps is not multithread safe.
SEE ALSO
mbsinit(3), wcsrtombs(3)
Linux man-pages 6.9.1 2024-06-15 wcrtomb(3)
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