生成任意一个国家的IP地址段

根据ISO 3166查询所需国家的2字母代码：https://www.iso.org/obp/ui/#search/code/，比如泰国的就是TH

根据不同的地区，下载各地的IP地址段列表文件：
https://ftp.arin.net/pub/stats/arin/delegated-arin-extended-latest
https://ftp.ripe.net/ripe/stats/delegated-ripencc-extended-latest
https://ftp.apnic.net/stats/apnic/delegated-apnic-extended-latest
https://ftp.lacnic.net/pub/stats/lacnic/delegated-lacnic-extended-latest
https://ftp.afrinic.net/pub/stats/afrinic/delegated-afrinic-extended-latest

cat delegated-apnic-extended-latest | awk -F '|' '/TH/&&/ipv4/ {print $4 "/" 32-log($5)/log(2)}' | cat > ipv4_th.txt