Pasted

user@host:/path/to/NIX/ubuntu/20.04.4$ isoinfo -d -i ubuntu-20.04.4-live-server-amd64.iso | awk '/^Volume\ size\ is:/ { print $4 "*2048"; }' | bc
1331691520
user@host:/path/to/NIX/ubuntu/20.04.4$ ls -l ubuntu-20.04.4-live-server-amd64.iso
-rw-r--r-- 1 user user 1331691520 фев 23 12:27 ubuntu-20.04.4-live-server-amd64.iso
# for real use in dd if=/dev/sr0 bs=2048
user@host:/path/to/NIX/ubuntu/20.04.4$ isoinfo -d -i /dev/sr0 | awk '/^Volume\ size\ is:/ { print $4; }'
user@host:/path/to/NIX/ubuntu/20.04.4$ dd if=/dev/sr0 bs=2048 count=`isoinfo -d -i /dev/sr0 | awk '/^Volume\ size\ is:/ { print $4; }'` | sha512sum -b