cpp/io/c/fclose

Closes the given file stream. Any unwritten buffered data are flushed to the OS. Any unread buffered data are discarded.

Whether or not the operation succeeds, the stream is no longer associated with a file, and the buffer allocated by std or std, if any, is also disassociated and deallocated if automatic allocation was used.

The behavior is undefined if the value of the pointer is used after  returns.

Return value
on success, eof otherwise