Buffer implements double buffering and can be used to keep backup tapes
 streaming or printers printing. It can also be used to convert a data
 stream to a given output blocksize.
 .
 Buffer uses shared memory to convert a variable input data rate to a
 constant output data rate. It is typically used in a pipe between a backup
 program and the tape device, but there are also other applications like
 buffering printer data in lpd's input filter.