whois is an open source, completely free and intelligent command-line software implemented in Perl and designed from the ground up to allow users to query domain names and IP addresses directly from any Terminal app under GNU/Linux operating systems.
An intelligent whois client for Linux
The software has been initially written in 1999 as an intelligent whois client for Linux operating systems. Since then, many features were added, such as support for all protocol extensions, including RIPE, CRSNIC and 6bone, as well as support for the IPv6 protocol.
The software is capable of automatically selecting the right whois server for most queries. In addition, it can query the right registry for many domains and netblocks, and includes an up-to-date database.
Like most command-line programs, whois comes with various options, which can be viewed at a glance, along with the usage message, by running the ‘whois --help’ command in a terminal emulator app. Most of its command-line options are flags supported by the whois.ripe.net website, as well as other RIPE-like servers.
Among these, we can mention the ability to connect to a specific server, to find the one level less specific match, to find all levels less specific matches, to find all one level more specific matches, to find all levels of more specific matches, to find the smallest match containing a mnt-irt attribute, to find an exact match, as well as to only look for objects of a certain type.
Additionally, you can force the program to display local copy of the domain objects even if it contains referrals, to search all the mirrored databases, to request a template for a specific object type, to request a verbose template for a certain object type, to turn off recursive lookups for contact information, and to search the database mirrored from a specified source.