grepcidr by Charly's Column

Although Linux has many grep variants, you can always find a new one. I only discovered grepcidr [1] a few months ago. As the name suggests, the tool filters input by IP addresses and networks. It works equally well with IPv4 and IPv6. To show grepcidr's capabilities, I will use it to compile a list of all IPv4 addresses on my home network. I got this from the Syslog on the firewall, which is also the DHCP server:

cd /var/log
grepcidr 10.0.0.0/24 syslog|grep DHCPACK|tail -n 1500|cut -f9 -d" "|sort|uniq > 1stlist

REF: http://www.linux-magazine.com/Issues/2018/216/The-sys-admin-s-daily-grind-grepcidr