{"id":53,"description":"regex: filter ipv4 address","tags":["linux","tools","regex"],"contents":["# regex pattern to filter IPv4 addresses","# upto 3 digits followed by ., repeated 3 times and up to 3 digits","# this is too generic. so invalid IPs like 333.232.444.999 would also be considered valid","ifconfig | egrep -o '([0-9]{1,3}\\.){3}[0-9]{1,3}'","# To search for only valid IP addr and output only the IP addr","ifconfig | egrep -o '((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)'","# Skip localhost and subnet masks","ifconfig | egrep -o '((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)' | egrep -v '^255|127.0.0.1'"]}