Shell Programming and Scripting

awk -F, ' NR>1 && $1=="a" {                                             # If current record no > 1 (for skipping header) and 1st field == "a"
  f=1;                                                                  # Set flag variable f = 1
  split($0,a,",");                                                      # Split current records using field separator: , and store in array var: a
} f==1&&$1=="b" {                                                       # If flag variable f == 1 and first field == "b"
  print sqrt(((a[4]+$4)^2)+((a[5]+$5)^2)+((a[6]+$6)^2)+((a[7]+$7)^2));  # Do arithmetic op using array values stored earlier & current record values
  f=0;                                                                  # Reset flag variable back to f = 0
}' filename

awk -F, '
$2 == 6{
    split($0,a,",")
    getline
    if ($2 == -6) {
       print sqrt(    \
        ((a[8] +$8 )^2) + \
        ((a[9] +$9 )^2) + \
        ((a[10]+$10)^2) + \
        ((a[11]+$11)^2))
    }
}' infile