Rgxg (ReGular eXpression Generator) is a command-line tool to generate (extended) regular expressions.

It can be useful to generate (extended) regular expressions to match for instance a specific number range (e.g. 0 to 31 or 00 to FF) or all addresses of a CIDR block (e.g. 192.168.0.0/24 or 2001:db8:aaaa::/64).