Bar is a simple tool to process a stream of data and print a display for the
user on stderr showing (a) the amount of data passed, (b) the throughput of the
data transfer, and, if the total size of the data stream is known, (c)
estimated time remaining, percent complete, and a progress bar. Bar was
originally written for the purpose of estimating the amount of time needed to
transfer large amounts (many, many gigabytes) of data across a network.
(Usually in an SSH/tar pipe.)