ввод символов (character input)
Возвращаемое значение (Return value)
Upon successful completion, these functions shall return the
number of successfully matched and assigned input items; this
number can be zero in the event of an early matching failure. If
the input ends before the first conversion (if any) has
completed, and without a matching failure having occurred, EOF
shall be returned. If an error occurs before the first conversion
(if any) has completed, and without a matching failure having
occurred, EOF shall be returned and errno shall be set to
indicate the error. If a read error occurs, the error indicator
for the stream shall be set.
