MD5 progress output - BASH

Question

I got a simple MD5SUM script in the works. Its pretty much done except for the part that displays the progress (percent of the file that's been calculated to the user). I'm thinking of using a while loop w/ a dummy variable that checks if the MD5 has been calculated. The only problem is that md5sum (on linux) doesn't return any kind feedback, except when the actual md5sum has been calculated. So, its difficult to show the users how much of the file has been processed. Here's a copy of the script.

#!/bin/bash

#MD5 verification tool
#1st argument is file name of .iso, and the 2nd argument is the the MD5 hexsum.

echo Checking file $1 .....  
#calc md5 for file
SUM=`md5sum $1`
#insert while loop here?
#compare values
test $SUM = $2 && echo original || echo False 

#8cd98b693ce542b671edecaed48ab06d8c
# GNOME-64.iso

exit 0

Answer 1

Use pv, installable on all major distros. SUM=$(pv "$1" | md5sum) will show a pretty progress bar with throughput and everything, something like:

bash> pv /media/secondary/backups/2013_01_12/* | md5sum
10.2GB 0:01:32 [ 115MB/s] [====>                 ] 19% ETA 0:06:21