### 2.42 `wcsrtombs`, `wcsnrtombs`—convert a wide-character string to a character string

Synopsis

         #include <wchar.h>
         size_t wcsrtombs(char *__restrict dst,
             const wchar_t **__restrict src, size_t len,
             mbstate_t *__restrict ps);

         #include <wchar.h>
         size_t _wcsrtombs_r(struct _reent *ptr, char *dst,
             const wchar_t **src, size_t len,
             mbstate_t *ps);

         #include <wchar.h>
         size_t wcsnrtombs(char *__restrict dst,
             const wchar_t **__restrict src,
             size_t nwc, size_t len,
             mbstate_t *__restrict ps);

         #include <wchar.h>
         size_t _wcsnrtombs_r(struct _reent *ptr, char *dst,
             const wchar_t **src, size_t nwc,
             size_t len, mbstate_t *ps);

Description
The `wcsrtombs` function converts a string of wide characters indirectly pointed to by src to a corresponding multibyte character string stored in the array pointed to by dst. No more than len bytes are written to dst.

If dst is NULL, no characters are stored.

If dst is not NULL, the pointer pointed to by src is updated to point to the character after the one that conversion stopped at. If conversion stops because a null character is encountered, *src is set to NULL.

The mbstate_t argument, ps, is used to keep track of the shift state. If it is NULL, `wcsrtombs` uses an internal, static mbstate_t object, which is initialized to the initial conversion state at program startup.

The `wcsnrtombs` function behaves identically to `wcsrtombs`, except that conversion stops after reading at most nwc characters from the buffer pointed to by src.

Returns
The `wcsrtombs` and `wcsnrtombs` functions return the number of bytes stored in the array pointed to by dst (not including any terminating null), if successful, otherwise it returns (size_t)-1.

Portability
`wcsrtombs` is defined by C99 standard. `wcsnrtombs` is defined by the POSIX.1-2008 standard.