Using AWK how can I total lines that match?

I'm trying to total the value of lines matching nvme* hhd from iostat in megabytes then awking to get total from line x to line z, in my case 2 lines.

iostat -m  <-- in megabytes

iostat -m |  awk '{if($1 ~ /nvme*/ ) print $2, $3, $4}'

------------------
9.38,   0.20,  0.57

13.67,  0.01,  1.60
------------------- 
23.05, 0.21, 2.17  <<-- The total

How can I achieve this?

Solution

Try:

iostat -m |  awk '$1 ~ /nvme*/{a+=$2;b+=$3;c+=$4;print $2, $3, $4} END{print"--------------";print a,b,c}'

How it works

$1 ~ /nvme*/

This selects the lines whose first field matches the regex nvme*. My iostat produces no lines that contain nvme. Consequently, it is up to you to determine if this is really the right regex for your case.
a+=$2;b+=$3;c+=$4

This keeps a running sum of the three columns of interest in the variables a, b, and c.
print $2, $3, $4

This prints the three columns of interest.
END{print"--------------";print a,b,c}

After all lines have been read in, this prints out the total. The print"--------------" produces a nice looking table on my system. If your iostat produces output in a different format, you may need to adjust accordingly.