Group domain counts by main domain.

README.md

Data

123 oh.duh.se
9000  duh.se

Output

9123 duh.se 

count_and_group_by_main_domain.awk

#!/usr/bin/awk -f
BEGIN { FS = "[.\t]" }
{
  domain = $(NF-1) "." $NF
  domains[domain] = domains[domain] + $1
}
END {
  for (domain in domains)
    print domains[domain] "\t" domain
}