checksum tar

Ever wanted to checksum a tar file as you write it to tape so that you can confirm the tar file without re-reading your data off disk?

First, create a tiny script called tarsum.sh

#!/bin/bash
tee >(md5sum > chksum.txt)

Then you can do

tar --use-compress-program tarsum.sh -cvf /dev/st0 mydir > filelist1.txt 2>&1
mv chksum.txt chksum1.txt
mt -f /dev/st0 rewind
tar --use-compress-program tarsum.sh -tf /dev/st0 > filelist2.txt
mv chksum.txt chksum2.txt
diff chksum1.txt chksum2.txt
diff filelist1.txt filelist2.txt