Calculating total size of disks

#bash #awk #grep

This is the output of lsblk command on my Ubuntu machine:

$ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
loop0    7:0    0   1.7G  1 loop /snap/0ad/592
...
sda      8:0    0 111.8G  0 disk 
├─sda1   8:1    0   619M  0 part /boot/efi
├─sda2   8:2    0   954M  0 part [SWAP]
└─sda3   8:3    0 110.3G  0 part /home
sdb      8:16   0 931.5G  0 disk 
└─sdb1   8:17   0 931.5G  0 part /
sr0     11:0    1 383.5M  0 rom

I wanted to get total size of disks sda and sdb together, but I wanted to use bash to do it.

First, I only get lines beginning with sda or sdb:

$ lsblk | grep -Pi '^sda|^sdb'
sda      8:0    0 111.8G  0 disk 
sdb      8:16   0 931.5G  0 disk

Then we isolate just the fourth column delimited by spaces (that is SIZE column).

$ lsblk | grep -Pi '^sda|^sdb' | awk '{print $4}'
111.8G
931.5G

Next step would be to add 111.8G and 931.5G together. So we do that:

$ lsblk | grep -Pi '^sda|^sdb' | awk '{print $4}' | awk '{total+=$1} END {printf "%.1fG\n",total}'
1043.3G

Lastly, let's convert the answer to terabytes (since the answer is in gigabytes):

logan@logan-mainPC:~$ lsblk | grep -Pi '^sda|^sdb' | awk '{print $4}' | awk '{total+=$1} END {printf "%.1fG\n",total}' | awk '{terabyte=$1/1000; printf "%.1fT\n",terabyte}'
1.0T

So we conclude that 1043.3G is about 1T in size. Now we know that we would need at least 1T of space to copy the contents of both sda and sdb to another hard disk. :)