wcsrtombs - Man Page

convert a wide-character string to a multibyte string


Standard C library (libc, -lc)


#include <wchar.h>

size_t wcsrtombs(char dest[restrict .len], const wchar_t **restrict src,
                 size_t len, mbstate_t *restrict ps);


If dest is not NULL, the wcsrtombs() function converts the wide-character string *src to a multibyte string starting at dest. At most len bytes are written to dest. The shift state *ps is updated. The conversion is effectively performed by repeatedly calling wcrtomb(dest, *src, ps), as long as this call succeeds, and then incrementing dest by the number of bytes written and *src by one. The conversion can stop for three reasons:

If dest is NULL, len is ignored, and the conversion proceeds as above, except that the converted bytes are not written out to memory, and that no length limit exists.

In both of the above cases, if ps is NULL, a static anonymous state known only to the wcsrtombs() function is used instead.

The programmer must ensure that there is room for at least len bytes at dest.

Return Value

The wcsrtombs() function returns the number of bytes that make up the converted part of multibyte sequence, not including the terminating null byte. If a wide character was encountered which could not be converted, (size_t) -1 is returned, and errno set to EILSEQ.


For an explanation of the terms used in this section, see attributes(7).

wcsrtombs()Thread safetyMT-Unsafe race:wcsrtombs/!ps


C11, POSIX.1-2008.


POSIX.1-2001, C99.


The behavior of wcsrtombs() depends on the LC_CTYPE category of the current locale.

Passing NULL as ps is not multithread safe.

See Also

iconv(3), mbsinit(3), wcrtomb(3), wcsnrtombs(3), wcstombs(3)

Referenced By

mbsinit(3), wcrtomb(3), wcsnrtombs(3), wcstombs(3).

2023-10-31 Linux man-pages 6.7