The fputwc() function writes the character corresponding to the wide-character code wc to the output stream pointed to by stream, at the position indicated by the associated file-position indicator for the stream (if defined), and advances the indicator appropriately. If the file cannot support positioning requests, or if the stream was opened with append mode, the character is appended to the output stream. If an error occurs while writing the character, the shift state of the output file is left in an undefined state.

The st_ctime and st_mtime fields of the file will be marked for update between the successful execution of fputwc() and the next successful completion of a call to fflush(3C) or fclose(3C) on the same stream or a call to exit(2) or abort(3C).

The putwc() function is equivalent to fputwc(), except that it is implemented as a macro.

The call putwchar(wc) is equivalent to putwc(wc, stdout). The putwchar() routine is implemented as a macro.

Upon successful completion, fputwc(), putwc(), and putwchar() return wc. Otherwise, they return WEOF, the error indicator for the stream is set, and errno is set to indicate the error.

The fputwc(), putwc(), and putwchar() functions will fail if either the stream is unbuffered or data in the stream's buffer needs to be written, and:

EAGAIN

The O_NONBLOCK flag is set for the file descriptor underlying stream and the process would be delayed in the write operation.

EBADF

The file descriptor underlying stream is not a valid file descriptor open for writing.

EFBIG

An attempt was made to write to a file that exceeds the maximum file size or the process's file size limit; or the file is a regular file and an attempt was made to write at or beyond the offset maximum associated with the corresponding stream.

EINTR

The write operation was terminated due to the receipt of a signal, and no data was transferred.

EIO

A physical I/O error has occurred, or the process is a member of a background process group attempting to write to its controlling terminal, TOSTOP is set, the process is neither ignoring nor blocking SIGTTOU, and the process group of the process is orphaned.

ENOSPC

There was no free space remaining on the device containing the file.

EPIPE

An attempt is made to write to a pipe or FIFO that is not open for reading by any process. A SIGPIPE signal will also be sent to the process.

The fputwc(), putwc(), and putwchar() functions may fail if:

ENOMEM

Insufficient storage space is available.

ENXIO

A request was made of a non-existent device, or the request was outside the capabilities of the device.

EILSEQ

The wide-character code wc does not correspond to a valid character.

Functions exist for the putwc() and putwchar() macros. To get the function form, the macro name must be undefined (for example, #undef putc).

When the macro form is used, putwc() evaluates the stream argument more than once. In particular, putwc(wc, *f++) does not work sensibly. The fputwc() function should be used instead when evaluating the stream argument has side effects.

See attributes(5) for descriptions of the following attributes:

exit(2), ulimit(2), abort(3C), fclose(3C), ferror(3C), fflush(3C), fopen(3C), setbuf(3C), attributes(5)