May 26, 2018
Filter IP addresses matching IPv4 CIDR/network specification
grepcidr can be used to filter a list of IP addresses against one or more Classless Inter-Domain Routing CIDR specifications, or arbitrary networks specified by an address range. As with grep, there are options to invert matching and load patterns from a file. grepcidr is capable of comparing thousands or even millions of IPs to networks with little memory usage and in reasonable computation time.
grepcidr has endless uses in network software, including mail filtering and processing, network security, log analysis, and many custom applications.