|file-length stream||[Generic Function]|
Return the length of the file that the stream is open to. The length is measured in units of bytes for binary streams and in units of characters for character streams, and is defined as the number of bytes or characters returned by read-byte or read-char when reading from the start to the end of the file. The caller is expected to firstly write and finish any buffer output, but it is also recommended that file-length methods flush any pending buffered output in case the caller fails to do so and calling the function ext:flush-output it typically appropriate. A default method for the class stream does nothing and returns nil.