I wanted to write about this as I learnt it recently.
But Bharathi has already done it.
http://bharathi.posterous.com/one-day-one-gnulinux-command-pv
simple usage:
$ pv foo.iso | sha1sum
It shows ETA, percentage and time elapsed and many other things.
I use it in my ISO installer to show the progress of installation.
Since I use Perl nCurses I wanted a tool to show progress with my own interface
but data should come from elsewhere in the backend.
pv has a -n switch which gave me just the percentage, so I used it and got my
job done.
I was very happy. ;)
-Girish
--
Gayatri Hitech
http://gayatri-hitech.com