FPUTWC
NAME SYNOPSIS DESCRIPTION RETURN VALUE ERRORS CONFORMING TO SEE ALSO NOTES
fputwc - write a wide character to a FILE stream
#include wc, FILE* stream); wint_t putwc (wchar_t wc, FILE* stream);
The fputwc function is the wide-character equivalent of the fputc function. It writes the wide character wc to stream. If ferror(stream) becomes true, it returns WEOF. If a wide character conversion error occurs, it sets errno to EILSEQ and returns WEOF. Otherwise it returns wc.
The putwc function or macro functions identically to fputwc. It may be implemented as a macro, and may evaluate its argument more than once. There is no reason ever to use it.
The fputwc function returns wc if no error occurred, or WEOF to indicate an error.
Apart from the usual ones, there is
EILSEQ
Conversion of wc to the stream's encoding fails.
ISO/ANSI C, UNIX98
The behaviour of fputwc depends on the LC_CTYPE category of the current locale.
In the absence of additional information passed to the fopen call, it is reasonable to expect that fputwc will actually write the multibyte sequence corresponding to the wide character wc.